Method of evaluating a storage medium by recirculating a test sample of a signal

ABSTRACT

Method for evaluating the quality of audio and/or video transfer characteristics of a device upon which, or through which, audio and/or video information is contained, or passes, respectively. The method concerns the evaluation of the quality of information transfer in the recording and playback of a recording medium or in the transferring of audio and/or video information through an information handling device referred to as a throughput device. Unit evaluation includes establishing an input signal of known content, measuring selected parameters of selected parts of the input signal, feeding the input signal to the unit under test, measuring the parameters of parts of the output signal from the unit corresponding to the same selected parts of the input signal, and comparing the selected parameters of the input signal with the corresponding parameters of the output signal. Whether monitoring the quality of the signal transfer characteristics of a throughput device, a magnetic tape containing program material, or a video disc, master disc or replica, a &#34;signature&#34; is created for the unit under test, and subsequent analysis of the unit as it progresses along a production line or of a copy made on the same or alternate recording medium results in a second &#34;signature&#34; which is compared against the first signature to make a determination of the quality of the signal handling or transfer characteristics of the unit. Thus out-of-tolerance conditions are automatically detected, thereby eliminating subjectivity and providing consistency in the quality level of device testing.

This application is a division of application Ser. No. 339,011, now U.S.Pat. No. 4,746,991, filed Jan. 12, 1982.

FIELD OF THE INVENTION

This invention relates to the evaluation of the quality of audio and/orvideo transfer characteristics of a device upon which, or through which,audio and/or video information is contained, or passes, respectively.Thus, the invention concerns both method and apparatus for evaluatingthe quality of information transfer in the recording and playing back ofa recording medium or in the transferring of audio and/or videoinformation through an information handling device referred to herein asa "throughput" device. Accordingly, this invention can be effective inthe evaluation of a recording medium per se, of the quality of transferof information contained on one recording medium to a similar or anotherrecording medium, or of a throughput electronic apparatus such as anamplifier or other signal processing apparatus through which audioand/or video information passes.

DESCRIPTION OF THE PRIOR ART

The art of performing a variety of audio and/or video tests on variouselectronic information handling devices is well known. It is anadditionally well-known technique to perform certain audio and/or videotests upon virgin recording mediums such as magnetic tape in order toevaluate the characteristics of the tapes for purposes of qualityassurance and for grading, i.e. for categorizing the quality as to gradeof the tapes exiting a production line.

Generally, such testing is done by employing manual testing techniquesor semiautomatic testing equipment. It is not uncommon, for example, ina magnetic tape manufacturing plant to periodically pull off of theproduction line a sample of the product being produced. A technicianthreads the tape on a rather conventional tape recorder/player and, bymanually manipulating buttons and knobs of the test equipment and makingthe appropriate connections on a patch panel or cable matrix, sets updifferent tests to be performed. Because of the need for allowingstandard test equipment to settle and accounting for human reaction timeto gather and record the information indicated on some sort of anindicating device, each test is performed for several seconds, oftentens of seconds. As test signals are applied to the tape, various testinstruments such as voltmeters, frequency counters, signal analyzers,etc., are employed to measure the characteristics of the appliedsignals. The tape is then rewound, the patch panel or cable matrix isset up differently for inputting to the test equipment the informationderived from the recorded tape on playback, and the measurements aremade again, this time of the recovered recorded signals. Test resultsare either manually written down, used as a basis for a go-no-goevaluation by the technician, or printed out on a high-speed lineprinter for later evaluation. In any case, not only do the tests requireseveral minutes of a test technician's time, but the test results maynot be known until after additional delays are encountered in theanalysis of test measurement print out.

Generally, complete testing of one parameter is made before setting upthe equipment to test another parameter. For example, an oscillator maybe used to apply a constant test tone to a tape for purposes ofmeasuring phase amplitude, signal-to-noise characteristics, and harmonicdistortion, and a standard voltmeter or frequency sensitive voltmeter isused as a measuring instrument. To perform the further test of frequencyresponse, a sweep generator is substituted for the oscillator, and aspectrum analyzer is substituted for the voltmeter. Thus, considerabletime is needed to make the change of connections for each different kindof measurement.

Furthermore, tests are often performed and evaluated against vaguelydefined standards. For some characteristics of a recording medium,especially involving prerecorded video tapes and video discs, thepreferred form of testing is by way of subjective listening or observingby unskilled persons who listen to speakers or look at televisionmonitors in an attempt to detect certain defects which perhapsinstruments could not detect, which would require an impractical numberof tests or instruments, or which would require an impractical length ofmeasurement time to perform. Obviously, this type of testing can resultin passing a run of prerecorded magnetic tape or a batch of prerecordedvideo discs containing defects due to the lack of complete attention bythe unskilled human monitors who, understandably, cannot be expected togive 100% attention to the quality of the material they are hearingand/or seeing.

Furthermore, as implied by the above-described methods of testing,manual testing or even semiautomatic testing is extremely time consumingand expensive when each type of test requires its own dedicated testequipment, and the problem is even more extreme when more than onelocation on the magnetic tape or disc is to be evaluated.

While semiautomatic devices are known for measuring and comparing inputversus output information, even with such equipment, it is oftennecessary to test only one isolated location on a tape or disc, andsequencing of testing for different parameters were, in the past, veryslow or manually performed.

While the above described exemplifies the sample testing of blankmagnetic recording tape and the post-recording evaluation of prerecordedtapes and discs, the same kinds of problems, expenses, and time delaysare encountered in the testing of virtually all other recording mediumssuch as magnetic, laser, and grooved discs. In the case of phonographrecords and grooved video discs, even further delays are expected due tothe (from a testing viewpoint) inordinate length of time between thepressing of the record or disc and the testing of same.

Furthermore, the tests referred to above for sample testing of blanktapes in a production run are performed for purposes of evaluating themagnetic characteristics of the medium only and are performed underideal recording and playback conditions resulting in specifications forthe medium per se. In other words, in the production of audio magnetictape, for example, the test results give an indication of the quality ofthe magnetic material deposited on the plastic backing such that themanufacturer can guarantee specific limits for such things ascoercivity, flux density, drop-out characteristics, etc. When the userof the tape records his or her programs, the copy can be evaluated bythe methods described above or by listening or viewing, and the user isconforted by the guaranteed specification of a previously tested sampletape taken off the production line. It is important to note here thatsuch testing (of a recording medium per se) done prior to this inventionhad little to do with characterizing the program transfercharacteristics of a recording medium, i.e. the quality of transfer ofprogram material during the recording/playback process. Rather, suchtesting ultimately resulted in published magnetic properties for thetape so tested. That is, the characteristics of the tape can beguaranteed by specification to the user, but the quality of theinformation to be stored and subsequently played back on the recordingmedium could only be gauged by manually monitoring a program played backafter recording or by reference to the magnetic properties of therecording medium as compared with the magnetic properties of othermediums and the prior experience of the user. A person in the businessof tape duplication or disc manufacture could only duplicate, typicallyto lesser standards, the kind of testing that the tape manufacturerperformed at the outset. Thus, a tape duplicator could record on a testtape certain test signals and subsequently measure the results similarto the manner in which the same was accomplished at the tapemanufacturing plant. However, this kind of testing is substantially aduplication of effort and is performed by a tape duplicator primarily asan update check on the duplicating equipment and not for the purposes ofevaluating the information transfer characteristics of the recordingmedium in the recording/playback process.

There are no tests performed at a duplicating facility on a previouslyrecorded program since all testing, as indicated above, is performed ona blank test tape sampling, and a user (or customer's) program materialis subsequently recorded at a recording studio on a presumably goodquality recording medium. Spot checking of the recorded informationafter duplication of the user's program by listening and observing amonitor screen has in the past been accepted as satisfactory, since sucha procedure represents the state of the art and is rather common in theduplication of magnetic tape, in the production of phonograph records,in the production of video discs, and in the production of duplicatefilm copies, as well as in any combination of tape/film/disc transfers.

Using magnetic tape as an example again, test signals of the typedescribed above are deposited using prior art procedures on a blank tapeand at arbitrarily chosen locations. There is no start or stop orlength-of-test data inserted on the test tape, and for that matter noneis needed. Since testing is performed on a blank tape, there is no needto fear destroying a previously recorded program, and therefore where onthe tape such tests are made, or how long on the tape such testingprocedures extend, is of little or no consequence. Furthermore, sincethe testing described above was, in the past, performed on blank tapepulled from a production line, due to the handling of the tape by thetechnicians, the tape after evaluation was considered to be unsaleable,and the tested units were discarded, resulting in waste.

Since the test procedures noted above are for evaluating the recordingmedium itself, there were heretofore no procedures known for evaluatinga medium which had material prerecorded on it and for subsequentlycomparing the results of such evaluation with the evaluation of aduplicate copy recorded on another storage medium.

Likewise, no procedures were known for depositing (encoding) testsignals on the lead-in/lead-out portions of a medium containingprerecorded program material. As noted above, because the testingprocedures of the prior art required a substantial length of time toperform, it would be considered impractical, if not impossible, to usethe lead-in and lead-out portions of a prerecorded tape to make certainperformance tests. Furthermore, those minimal tests that were performedon the prerecorded tape in the past involved the observance of testsignals deposited at the time the master program was recorded torepresent the conditions of recording at the time the master tape wasmade. That is, when the master tape was to be duplicated, reproduced, orset up for cutting a disc, audio tones at the beginning of the tape wereused to set level and frequency response characteristics of the playbackunits so that they would match corresponding characteristics of therecording equipment. Similarly, in the video portion of a video tapeprogram, a color bar pattern is often inserted at the lead-in on amaster tape, but this again is used to align the playback equipment tomatch the recording equipment. For example, the chrominance level, videolevel, and hue can be adjusted upon playback by observing such a testpattern on a video monitor. Presumably, the same parameters of theprogram material to follow will then be played out properly. Again,however, the procedures described for depositing and recovering audioand/or video information from the lead-in of a prerecorded master tapewere not for the purposes of evaluating the transfer of information inthe record/playback process of another generation of program material,but rather to align the equipment at the duplicating facility with thecharacteristics of the equipment at the recording facility.

Of course, part of the need for adjusting levels at the duplicatingfacility results from the losses in quality during the recording of theuser's program. However, it is important to note that, whether theuser's program is audio or video in nature, the user's program on thetape is a result of a mixdown and/or editing activity, and the lead-inaudio test tones or video test signals are merely a part of the overallinformational content of the tape supplied by the user (customer).Duplicating the material from the user's tape, then, follows theprocedure of first aligning the audio and/or video duplicating equipmentusing the test signals in order to match, to the extent possible, thecharacteristics of the orginal recording equipment upon which the masterwas prepared, and secondly transferring the information after thelead-in test signals so that the final duplicate product would be voidof the test signals and contain only program information copied from theuser's master tape. It would not be wise to transfer the test signalsalong with the user's program, since the user would then hear or observethe undersirable test signals, and this would be a distraction to him orher. Thus, this is consistent with the use to which the test signals areput, as discussed above, and renders either impractical or undesirablethe transferring of the test signals on the user's tape to the duplicatecopy or replica.

Evaluating the transfer characteristics of audio and video amplifiersand the like is also common practice in the art of device testing. Suchtesting is of primary importance in production testing, qualityassurance, and component fault testing.

It is common practice, for example, to apply a reference input signal toa piece of electronic apparatus, or component part thereof, and tomeasure the output of the device to determine if it is within acceptablelimits. Such limits can be established by measuring a previously "knowngood" device or by establishing test limits according to acceptablestandards in the art or by calculation through "worst case" analysis.According to U.S. Pat. No. 3,946,212 to Nakao et. al., an automaticquality control system is disclosed in which an estimated value to beobtained from an unprocessed work piece, depending upon informationobtained from previously processed work pieces, is calculated and iscompared with a predetermined control limit. When the estimated value isbeyond the control limit, machine adjustment is called for, and aninstruction signal is generated to alert the operator.

Automatically comparing like devices is further exemplified in art byU.S. Pat. No. 3,471,779 to A. J. Ley which test like devices by applyingone complete cycle of a test input signal in the form of a periodic polyfunction of a substantial number of periods, and determining the RMSvalue of the error between the test input signal and the resultinglinearily related output signal from the apparatus under test. In thismanner, although the output versus input characteristics of the likedevices are not compared directly, an indication of the quality of theunit under test is accomplished by comparing input and output RMSvalues, and like devices are compared by comparing the output RMS valuesfor each device.

Other illustrations of comparing like units in the prior art can befound by reference to U.S. Pat. No. 3,651,315 to Collins which comparesdata combinations taken from a unit under test with the datacombinations of a "known good unit". According to Collins, suchcomparison can be made in digital format using a digital pseudo-randomgenerator in combination with a characteristic of the unit under test toproduce the set of data combinations compared with those of the "knowngood unit".

Another form of "like device" testing can be found in U.S. Pat. No.4,271,515 to Axtell, III et al. A reference unit output signal and anoutput signal of a unit under test are paired and selectively andsynchronously compared in response to a common input signal. Thecomparison is performed by means of substraction, producing an errorsignal which is compared against a limit window.

Another kind of unit testing can be found in another series of prior artpatents which compare the output of a unit under test with a referencesignal, as opposed to a "like device" as discussed above. Examples ofreference data comparison techniques are found in U.S. Pat. No.3,892,955 to Maejima in which output data obtained from a device undertest is compared against reference data contained in a programinstruction from a program control unit; in U.S. Pat. No. 3,673,397 toSchaefer which tests the output of a circuit under test against theoutput of a storage device previously stored with a prediction of theexpected response of the stimulus to be applied to a corresponding inputof the circuit under test; in U.S. Pat. No. 4,055,801 to Pike et al.which teaches the automatic testing of electronic equipment in a similarmanner as Schaefer, but under computer control, the evaluation by thecomputer being made against programmed standards; in U.S. Pat. No.4,266,292 to Regan et al. which tests for faults in an analog-to-digitalsection and a digital-to-analog section of a code converter in amultiplex telecommunications system; and in U.S. Pat. No. 3,916,306 toPatti in which the testing of complex electronic circuitry isaccomplished by exercising the inputs of a large scale integrationdevice under test and monitoring the output as compared with expectedoutput from the device under test and initiating a pass/failmanifestation upon the detection of an inappropriate comparison.

Detecting the analog signal degradation in channel bank apparatus isknown from U.S. Pat. No. 4,279,032 to Smith in which a plurality ofsequences of prescribed test code words are circulated via a loop-aroundpath bridging the receive and transmit path of a channel unit, and a setof values, each corresponding to a type of analog signal degradation, isderived for each recovered word sequence. The derived set of values isaveraged over the recovered sequences, and if any average characteristicvalue is not within an expected tolerance of a corresponding prestoredexpected average value, a defective channel unit indication isdisplayed.

Another particular type of reference data comparison can be found byreference to U.S. Pat. No. 3,142,820 to G. S. Daniels. The Danielstesting system continuously monitors the conditions of variables andrecords the values thereof by the use of scanning means for sequentiallyscanning a large number of variables in a predetermined order, and analarm detecting means for detecting alarm conditions by comparingsignals from transducers associated with the variables withpredetermined pre-set signals representing upper end lower alarm limitsof the variables. According to Daniels, the high and low alarm limits,as well as other factors such as gain and rear offset will be changedfor the variables individually or en masse and without interrupting thescanning or recording operations being performed.

In U.S. Pat. No. 4,194,113 to Fulks et al., a circuit board under testis compared to a corresponding known-correct response to identify afaulty output of the board under test. Fulks et al. defines theprovision of a main memory which stores a signature file containingknown-correct signatures for the nodes of a board under test. Asignature is generated for each node on the circuit board and iscompared to a corresponding known-correct signature for that node as itis probed by the operator to identify a faulty input node.

Finally, in the prior art disclosures concerning reference and "likeunit" comparison testing, reference is made to U.S. Pat. No. 4,184,205to Morrow and to U.S. Pat. No. 2,893,635 to L. G. Gitzendanner, both ofwhich define data acquisition systems which make use of the dataobtained from the units under test to create trend analyses.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide a method of,and means for, analyzing the signal transferring characteristics of asignal processing unit.

A further object of the invention is to perform a large number of audioand video measurements on the unit under test electronically todetermine out-of-tolerance conditions of the unit as a basis for passingor rejecting the unit in a production line.

A further object of the invention is to provide a unit evaluation methodand means as described above which will eliminate subjectivity andprovide consistency in the quality level of device testing.

Yet a further object of the invention is to provide automated producttesting of the type described above wherein a large number ofmeasurements are taken during testing and correlated within-processactivities in order to develop out-of-tolerance trends, improved producttrends, and to alert supervisory personnel of potential problems in theprocess so that appropriate corrective action can be taken beforepotential problems produce real ones. When fully implemented throughoutthe production line, potential problems can be pinpointed, analyzed, andcorrected in almost real-time, thereby eliminating or minimizingdowntime for the production line and significantly reducing scrap andwaste.

According to the invention, "unit evaluation" is accomplished byestablishing an input signal of known content, measuring selectedparameters of selected parts of the input signal, feeding the inputsignal to the unit under test, measuring the parameters of parts of theoutput signal from the unit under test corresponding to the sameselected parts of the input signal, and comparing the selectedparameters of the input signal with the corresponding parameters of theoutput signal.

In the following discussion, the term "unit" in the phase "unitevaluation" includes tapes, discs, audio records, electronic storage,various electronic circuits ranging from simple integrated circuits orprinted circuit boards to macrosize amplifiers or other complexinformation handling equipment. Accordingly, "unit evaluation" maycomprise the analysis of information recovered from a recording mediumor information sensed at the output of a "throughput" device,"throughput" being defined as a signal processing unit through which asignal is passed and processed, such as a pre-amplifier, amplifier,circuit board, etc.

Since this invention is exceptionally useful in the evaluation ofvideodiscs, a special form of the phrase "unit evaluation" will be usedthroughout this application, and thus, "disc evaluation" will refer tothe analysis of information retrieved from a videodisc as compared withthe analysis of the recording medium (generally tape) of which theinformation recorded on the disc is duplicative. Thus, "tape evaluation"will refer to evaluating the contents of a master tape, while "discevaluation" will refer to the information retrieved from a replicateddisc.

Another term used throughout this application is "signature". The term"signature" has been used in the prior art to designate a parameterlisting against which devices being tested are compared. Examples of theuse of the term "signature" can be found in U.S. Pat. No. 4,216,374 toLam et al., and U.S. Pat. No. 4,194,113 to Fulks, et al. In both priorart disclosures, however, the term "signature" refers to a specific andexactly predictable electronic state to be used as a test reference. Inthe Lam et al. Patent, the "signature" is a particular bit pattern, andthe unit under test when exercised in a specific manner must exhibit thesame bit pattern in order to be considered an acceptable unit. In theFulks, et al. Patent, the nodes are probed, and the signals at each nodeare verified to be accurate as compared with a "signature" by countingthe number of logic level transitions of the node under test orcomputing cyclic redundancy check characters. In the manner in which"signature" is used in the prior art, there is no identification of acharacteristic or personality of the unit under test as there would bein the traditional use of the term "signature". All that is required inthe prior art is that certain transitions occur at the proper time forthe unit under test, and if for a given input to the unit, a properresponse is noted, the unit is said to have conformed to the "signature"of a theoretical model.

In counter-distinction to the use of the term "signature" in the priorart, the term as used in this application does have a degree of identityor "personality" of the unit under test, insofar as the "signature" iscomprised of a multiplicity of test parameters, each parameter havinglimits within which comparable measurements of the unit under test mustfall. Accordingly, the "signature" as used with this invention is apracticle, as opposed to theoritical, model against which all furtherunits are compared. Thus, "signature" may account for degradation of aparameter in the recording/playback process of a magnetic tape, avideodisc, or a throughput device.

Accordingly, the pass/reject test for unit evaluation according to thesubject application is based upon undue degradation versus acceptablesignal fidelity in the analysis signal transfer through the unit.Because a large number of audio and video measurements on the unit areutilized in producing a "signature", exacting ranges for tolerancelimits can be established to produce quality units consistent withacceptable yield figures. Furthermore, the "signature" parameters ofthis invention are derived in analog fashion, and can therefore obtain avalue within a range of acceptable limits (as opposed to the meredetection or not of a digital logic level per the prior art), and such a"signature" can therefore account for system losses. For example, in theproduction of a videodisc, the reference "signature" is derived frommeasurement of the magnetic tape master from which a disc master isproduced. Hereinafter, the tape master from which a video disc master ismade will be referred to as a pre-mastering tape. Furthermore, aparticular "signature" can be established for each process step in themaking of the final videodisc, inclusive of transferring a customer'stape to a pre-mastering tape, exposing and developing a master disc,metalizing the master disc, producing a stamper from the master disc,producing a single disc half from the stamper, depositing a reflectivecoating on the disc half, adding a protective coating to the disc half,adhering two disc halves together, and final test after labeling andbefore packaging. In each of the steps, a different signature can beestablished, with each subsequent down-stream signature havingdifferent, usually wider, tolerance limits than the previous one. In theinjection molding of the disc half, for example, there are expectedlosses due to birefringerence, planing, contamination, etc. By studyingthe degradation of the "signature" as the product is produced, attentioncan be given those areas in the process which contribute most greatly tothe degradation of the product.

In addition to substantially "real-time" evaluation for correlation with"in-process" activities to provide alarm or reporting techniques toalert personnel in case of out-of-tolerance conditions, theout-of-tolerance parameter trends can be utilized to improve specificmanufacturing processes or process steps due to the highly accurate,repetitive, objective testing capabilities of the invention. Such"trend" information can be utilized to foresee potential problems eventhough the parameters tested at any given time is within exceptablelimits. For example, continuning wear or gradually soiling parts can bedetected by observing an unusual change in the "signature" parameters.

Additionally, the use of a "signature" in the manner used with thisinvention can become a valuable research and development tool. Forexample, on a pilot line incorporating the monitoring system accordingto this invention, certain process parameters can be changed, e.g.temperature, pressure, time, etc., in order to observe how the"signature" is effected by each process parameter change.

Moreover, because of the automatic and high speed of testing which willbecome evident in the further discussion of this invention, many unitsunder test can be simultaneously evaluated by a single operator. Asingle central controller can interrogate, through a plurality ofinterface subsystems, a similar plurality of audio/video test subsystemswith complete accuracy and repeatability of parameter testing. Thecentral controller is then adapted to retain the test results in itsmemory until recalled to be processed in a data evaluation subsystem andmade into a permanent record in a data readout device. This is in brightcontrast to the rather crude manual procedures in the past where asingle operator subjectively observes and listens to three or fourprograms simultaneously and makes on-the-spot evaluations with permanentrecords being solely in the form of simple notes or boxes checked on aform. Since evaluation of units by a different operator will involve atotally different subjective evaluation, it is clear that comprehensiveand accurate trend analysis is not possible. Furthermore, inconsistencyin the evaluation of the final product is unpredictable even for thesame operator on different days of employment.

Basically, the invention comprises a central controller with itsperipheral memory keyboard, and readout devices, and audio testsubsystem, a video test subsystem, and a data evaluation subsystem. Theunit under test in the examples of the following discussion will concernthe evaluation of a video disc, the informational content of which wastaken from a video tape. It will be understood that, in view of thelarge number of possibilities for application of the invention, thedescription will be simplified by referring primarily to the field ofproducing and testing video discs, although the application to othertypes of recording mediums and throughput devices will be evident asdescription details are given.

The central controller for the monitoring system of this invention canbe any one of a family of known small, high speed, computers thatprovide an array of peripheral equipment including disc storage devices,printers, display stations, and communications and interfacingcapabilities that are necessary for communicating with the audio, videoand evaluation subsystems.

The major steps in producing a video disc from a source material includepreparing a submaster tape from the customer's master tape whilesimultaneously depositing audio and video test signals before, during,and after the program material, analyzing the test signals and programmaterial on the tape, deriving a "signature" of the submaster tape,establishing tolerance limits for the parameter components of thesignature, transferring the audio and video information from thesubmaster tape to a video disc through process steps to be discussedlater, playing back the recorded disc and recovering test signalstherefrom to produce an output signature of the disc, comparing theoutput signature of the disc with the signature established from thesubmaster tape, and evaluating the comparison results and reading outdesired data gathered during data evaluation.

Audio test signals are depostied on the lead-in and lead-out portions ofthe submaster tape, i.e., on those portions of the submastering tapepreceding and following the program material, respectively. Uponplayback of the submaster tape or the disc, the audio test signals onlead-in and lead-out are analyzed and made part of the respectivesignatures for the tape and disc.

Additionally, audio and video measurements are made during the activeportion of the program material, the audio portion being analyzed forspectrum analysis during a prescribed time period, and a test is made ofthe audio channels of the recording medium to determine whether or not amonophonic of non-monophonic signal is contained in each of the(generally) two channels.

Finally, the video portion of the recovered signals from the recordingmedium are analyzed using the VITS and VIRS signals deposited in thevertical interval of the signal contained on the submaster tape andsubsequent disc program.

In a practical application, the audio test subsystem reads and makes 24audio measurements and/or tests on both channels or lead-in and lead-outof the pre-mastering tape. These measurements are compared withstandards, and if acceptable become part of a "signature" for theparticular tape. In addition, monophonic/non-monophonic testing andaudio spectrums are obtained at intervals throughout the active programarea and the data so obtained also becomes a part of the signature. Anumber of samplings of video measurements and/or tests are takenthroughout the active program area as indicated previously, and eachvideo sampling provides 45 measurements that are compared withstandards, and if acceptable also become a part of the tape's"signature". The audio and video measurements procedure just describedis termed "tape evaluation", and produces a printed report and a"signature" that may be retained for future use or transfered to anothermonitoring system via diskette or teleprocessing.

The monitoring system of this invention also provides the capability ofperforming the identical set of measurements on products subsequentlyproduced from evaluated tapes, e.g. other video tape copies or disccopies. The measurements, both audio and video, comprise an output"signature" which is compared with the evaluated tape's "signature", andexceptions are noted when any comparison exceeds tolerance limits. Thislatter procedure is termed "disc evaluation".

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail having reference to theappended drawings in which:

FIG. 1 shows in block diagram form a complete audio-video qualitymonitoring system in which a common central controller cooperates withmultiple interface subsystems and associated multiple audio-video testsubsystems;

FIG. 2 shows a modified version of FIG. 1 in which, rather than having acentral controller, the audio and video test subsystems communicate withand are under the control of an isolated and independent interfacesubsystem and controller;

FIG. 3 is a more detailed block diagram of the audio-video qualitymonitoring system of FIG. 1 showing the interrelationship between thecentral controller and one of the plurality of interface subsystems andits associated audio and video test subsystems;

FIG. 4 is a block diagram showing a further breakdown of the audio testsubsystem of FIG. 3;

FIG. 5 illustrates a representation of a length of video tape showingthe position of lead-in, lead-out program material, and track locationsfor audio and control and cue tracks;

FIG. 6 shows, in the upper half thereof, a special representation of theplacement of audio test tones at the lead-in and lead-out portion of avideo tape or video disc, and in the bottom half thereof, a pictorialrepresentation of the signals in the corresponding blocks of the tophalf of the figure;

FIG. 7 shows, in block diagram form, the audio test tone generator logicfor creating the audio test tones for placement on lead-in and lead-outof the video tape or video disc;

FIG. 8 is a timing diagram showing the audio test tone generationaccording to the test tone generation logic of FIG. 7;

FIG. 9 is a general block diagram illustration of the audio analysislogic portion of the audio test subsystem;

FIG. 10 illustrates a more detailed portion of the audio analysis logic,and in particular, the audio controller portion thereof;

FIG. 11 shows details of a portion of the audio analysis logic, and inparticular, the audio and video selector, 6734 tone detector, and timecode or frame number selector;

FIG. 12 shows the details of the multi-programmer portion of the audioanalysis logic of FIG. 9;

FIG. 13 is a timing chart showing the relationship between the signalsoperative for carrying out the audio analysis according to the logicdiagram of FIG. 9;

FIG. 14 illustrates, in block diagram form, the operative functionalblocks of the video test subsystem;

FIG. 15 shows a standard television waveform for two color fieldsrepresenting a single color frame according to NTSC standards;

FIG. 16 shows the waveform of the Composite VITS signal located in thevertical interval of the video portion of the active program material;

FIG. 17 shows the waveform of a Combination VITS signal located in thevertical interval of the video portion of the program material;

FIG. 18 shows the waveform of the VIRS signal also located in thevertical interval of the video portion of the program material;

FIG. 19 shows the waveform and specifications for a standard horizontalblanking pulse with corresponding synch pulse and color burst signal;

FIG. 20 is a waveform showing the theoretical waveform of FIG. 19 as itwould appear on an oscilloscope, and showing, more particularly, aflattened portion of the waveform on the back porch of the horizontalblanking pulse immediately following the color burst signal;

FIG. 21 is a pictorial representation of the distribution of points on avideo disc on which noise characteristics are measured;

FIG. 21B shows, in block diagram form the circuitry useful in measuringthe noise content on the back porch of the horizontal blanking pulse ofFIG. 20;

FIG. 22 is a general block diagram showing the video analysis logicassociated with the video test subsystem;

FIG. 23 is a general block diagram of the audio-video data evaluationsubsystem;

FIG. 24 is an overall procedural block diagram showing the manner inwhich tape evaluation is accomplished according to the presentinvention;

FIG. 25 is an overall procedural block diagram showing the manner inwhich the disc evaluation is accomplished according to the presentinvention;

FIG. 26 is an overall procedural block diagram showing the manner inwhich the throughput device evaluation is accomplished according to thepresent invention; and

FIG. 27 is an overall procedural block diagram showing the manner inwhich the digital signature evaluation is accomplished according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a complete audio/video quality monitoring system utilizinga central controller 1 and a plurality of terminals each comprising aninterface subsystem 3, an audio/video test subsystem 2, and the unitunder test 4 connected to the audio/video test subsystem 2. Thepheripheral equipment associated with the central controller 1 comprisesa memory unit 13, a keyboard 70, a data evaluation subsystem 19, and adata raadout device or devices 64.

The central controller 1 provides the hardware and software facilitiesnecessary for the subsystem control, data management, decision making,and reporting required of the audio/video quality monitoring system(hereinafter referred to as AVQMS). Memory unit 13 provides extensivestorage, preferably in the form of disc storage, to permit rapid accessto programs, signatures, and other data. The data readout device 64 canbe a single display station or may comprise a plurality of displaystations to permit the operator to observe communications from thecentral controller concurrently at different locations. Keyboard 70could be accessed at a single location or could be made available ateach data readout device 64. The keyboard is used to select options fromthe AVQMS main menu and respond to the prompts that are issued as aresult of each selection. Accordingly, complete control of the recordingequipment to deposit the test signals on the pre-mastering tape, controlof the operation of the units under test, and commands to the centralcontroller are systematically effectuated at the keyboard.

While FIG. 1 shows a single central controller 1 with multiple interfacesubsystems 3, an alternative to such a "centralized" system is thearrangement of FIG. 2 in which each interface subsystem 3 is inclusiveof its own, perhaps less sophisticated, controller, and has its ownmemory unit 13, keyboard 70, and data readout devices 64. FIG. 2 furthershows a slightly more detailed communication link between the variouscomponents of the interface, test, and evaluation subsystems. Thecommunication link 18, among other things, is used to request programload and start of execution by the interface subsystem and controller 3,send measurement data to the controller 3 from audio test subsystem 5,and communicate position data to and from the two units for carrying outthe recording and acquiring of data at specific locations designated bythe operator.

Link 20 is used to load the video measurement programs from thecontroller 3 to the video subsystem 7, send position data from thecontroller 3 to the video test subsystem 7, and transmit videomeasurement data from the video test subsystem 7 to controller 3.

Tape and/or disc position data is also provided between the unit undertest 4 and controller 3 through communication link 16.

Communication links 8 and 10 are, respectively, audio and video links toprovide subsystem control of the unit under test 4, and to transmit andreceive audio and video signals between unit under test 4 and therespective test subsystem.

FIG. 3 shows a greatly expanded version of the arrangement shown in FIG.1 with central controller 1 and its connected peripheral equipmentassociated with only a single interface subsystem 3, audio testsubsystem 5, video test subsystem 7, and unit under test 4. To thispoint, the unit under test 4 has been treated as strictly a player-typeunit capable of reproducing audio and video signals from a prerecordedtape or disc. The phrase "unit under test", however, carries with it,for the purposes of this application, a more complex arrangementcomprised of a tape recorder/player 11, a disc player 9, and an audioand video selector 53 as shown within the unit under test block 4 inFIG. 3. The disc player is capable of outputting both video and audiosignals to the selector 53 on lines 147 and 151, respectively.Similarly, the tape recorder/player 11 outputs video on line 149, andaudio on line 153. Later, it will be evident that the audio lines 151and 153 carry two lines of audio for the purposes of accomodating asterophonic or two channel signal.

Operation control, i.e., stop, play, reverse, fast forward, rewind,etc., is effected by operation control 117 in interface subsystem 3 viacable 133 shown in FIG. 3 as a single line for simplifying the drawing.Operation control is also effective to select either audio channel, orboth, and video from either the disc player 9 or tape recorder/player11. Audio and video are thus outputted on lines 58 and 118,respectively, leaving the audio and video selector 53. Since the audioand video test subsystems are capable of analyzing audio and videosignals from either the disc player 9 or tape player 11, in order tominimize the amount of test equipment in the test subsystems, the audioand video selector 53 is provided to select the audio and video fromonly one of the program sources at a time.

Tape position is outputted on the data channel output line of the tapeplayer 11, and audio test tones are applied to the tape by tape recorder11 as will be discussed in connection with more detailed figures later.

Having reference to FIGS. 3 and 4, the function of the audio testsubsystem will now be described. The description will carry through theprocess from receiving a master tape from a customer through tapepre-mastering (to produce a submaster tape), through disc mastering andreplication, and finally through tape and disc evaluation processes.

A customer's tape, referred to as a master tape, is not involved in theevaluation process for at least two major reasons, namely that a certainamount of lead-in and lead-out time is necessary preceding and followingthe program material, and customer's tapes are often devoid ofsufficient lead-in and lead-out tape lengths, and secondly priorhandling of the tapes have made the lead-in and lead-out portionsunusable for test purposes. Accordingly, upon receiving a customerstape, a duplicate is made, and while the duplicate copy is properlytermed a submaster, it is also referred to as a pre-mastering tapepreparatory to producing a disc master. In any event, the first step inthe process is to transfer the customer's program from the master tapeto a submaster or pre-mastering tape. Simultaneously with thetransfering of the video portion of the program to the pre-masteringtape, appropriate video test signals are inserted on lines 19 and 20 ofthe vertical interval. A timed sequence of audio test signals isrecorded at a pre-determined location on the lead-in and lead-outportions of the pre-mastering tape. The signals will be used to analyzethe audio quality of the signals recorded on the tape and on the disc tobe made from the tape. Details of the lead-in and lead-out audio testingwill now be discussed.

As indicated previously, audio measurements are taken on test signalsapplied to the lead-in and lead-out areas of the tape and of samplingsof the audio program throughout the active program area.

At the display station of the tape operator, the tape operator selectsthe test tone generation option from the AVQMS main menu. The operatorthen winds the tape to a point at least 1200 to 1500 frames in front ofthe active program area to define a start location in the lead-inportion of the tape. It is to be noted here that, since there is novideo program material available, it is not possible to determine tapeposition or frame number by decoding the frame code number in thevertical interval of the video signal. Accordingly, for purposes ofapplying test tones to lead-in and lead-out portions of the tape, SMPTEaudio time code is recorded on one of the audio channels or on the Qdata line of the tape recorder. By reading the SMPTE time code andcounting backwards for at least 1200 to 1500 frames, sufficient time isleft before the beginning of the program material to insert anapproperiate number of audio test tone signals.

In FIGS. 3 and 4, the data channel from the tape player 11 is outputtedon line 34 and is sent to time code selector 51, a second input of whichis a time code signal from time code register 116 as set up by thekeyboard 70 via central controller 1. The operator thus rewinds the tapeon recorder 11 to a position upstream of the start position for the testtones and sets the tape recorder into a recording mode through actuationof operation control 117 over line 133. When the time code on datachannel line 34 matches the time code from register 116, the time codeselector 51 sends an output compare signal to the audio controller 21which then initiates, over line 30, test tone generator 49 to apply testtones to both channels 1 and 2 of tape recorder 11.

In a similar manner, after the test tones have been applied to thelead-in portion of the tape, the operator performs a high speed tapewind to a point corresponding to the end of the active program andenters a second beginning point for the test tones to occur, duringlead-out of the tape, beginning at least 150 frames after the programend. Under control of central controller 1, when the operator permitsthe tape to resume normal speed prior to passing the end of activeprogram area, a match is again detected by time code selector 51 atleast 150 frames after the program end, the tape recorder is put intorecord mode, and the test tone generator 49 is enabled by audiocontroller 21 to deposit test tones on channels 1 and 2 of the taperecorded by tape recorder 11.

In the above description, the manner in which audio test tones areapplied to the lead-in and lead-out portions of a pre-mastering tapehave been described. It can be appreciated that certain programs lendthemselves to a format on the storage medium such that long periods ofdead time exist between program segments. For example, a musical groupmay produce a program in a form similar to that of present day audiodisc recording, i.e., with each song contained in a band on the disc. Ifa videodisc was prepared in the same manner, it is contemplated that thepresent invention can be utilized to insert audio test tones in betweenisolated program segments, as well as during lead-in and lead-outlocations. Such test signals contained between program segments will notbe an undue distraction to the listener and observer, since the testsignals will either be not visible or audible to the ultimate user orwill be sufficiently short in time duration that it will pass so quicklythat will be substantially un-noticable. In the discussions to follow,it well be evident that certain test signals are inserted during thevertical interval of the video signal, and the test tones just describedwill be confined within a time period equal to approximately 12 verticalframe time slots. Under NTSC standards, 12 picture frames would lastless than half a second. The advantage of inserting test tones betweenprogram segments is, of course, that more of the disc area can beverified for acceptable quality, although testing lead-in and lead-outareas of either the pre-mastering tape or the final videodisc productestablishes and extremely high confidence level in the overall qualityof the recorded material.

In any event, the method of characterizing the information transfercharacteristics of the recording medium basically involves recording andsimultaneously making a first measurement of, known values of one ormore test signals on the recording medium, followed by playing back therecording medium and making a second measurement of the recorded testsignal or signals. In the manner of establishing a "signature" as arepresentation of the signal transfer characteristics, and unlike priorart prodedures involving merely checking properties of the medium (e.g.,magnetic properties of a video tape), deviation levels from the firstmeasurement results are set up as prescribed tolerance limits for theaforementioned second measurement, and the results of the firstmeasurement are compared with the results of the second measurement todetermine if the second measurement results are within the prescribedtolerance limits established from the first measurement results.Although applying audio test tones to the lead-in and lead-out portionsof the tape have only been described heretofore, this manner ofcharacterizing the information transfer characteristics of a recordingmedium can involve the insertion and testing of video test signals aswell.

As also will be described later, the present invention can apply toanalyzing the signal transferring characteristics of a signal processingunit such as a throughput device by utilizing the same unique"signature" technique described in connection with evaluating therecording transfer characteristics of a recording medium. When testingthroughout devices, (such as amplifiers, printed circuit boards,microelectronic chips, etc.) or in gererally applying the presentinvention, analyzing the signal transferring characteristics of a signalprocessing unit can be accomplished by establishing an input signal ofknown content, measuring selected parameters of selected parts of suchinput signal, feeding that input signal to the signal processing unit,measuring the parameter of parts of the output signal from the signalprocessing unit correponding to the similar selceted parts of the inputsignal, and comparing the selected parameters of the input signal whiththe corresponding parameters of the output signal. Again, the tolerancelimits for the measurement of parameters of the output signal arederived as deviation levels from the measurement of the correspondingparameters of the selected parts of the input signal. Here again, thetolerance limits for the output signal, as deviations from acceptabletolerance limits established from measurements of the input signal,represents a unique "two tiered" characterization of the transfercharacteristics of the processing unit so as to establish anb identityof the processing unit according to a "signature" comprised of theaccepted deviation levels within which the parameters measured at theoutput of the processing must fall. This is a significant departure fromthe prior art test procedures in which an output signal parameter ismerely compared with a "shopping list" of calculated values.

Especially when testing the lead-in, lead-out, or inter-band portions ofa recording medium, it is important to have the visible or audible testsignals to be as short as possible so as to be substantiallyun-noticable to the ultimate user. Additionally, when inserting testsignals on lead-in and lead-out of a recording medium, the amount of"real estate" must be kept to a minimum, as there are fixed limitationson tape length and disc track capacity within which all test signals andprogram material must be confined. Moreover, since the present inventioncan advantageously be used to monitor the quality of videodiscs exitinga production line, it is essential that the amount of time necessary togather information from the pre-recorded disc be kept to an absoluteminimum. Thus, not only is the arrangement of FIG. 1 conducive to a highrate of product evaluation due to the multiplicity of audio/video testsubsystem arrangements, but each test subsystem can be, utilizing afeature of the present invention, adapted to quickly gather informationfrom a unit under test, store that information, and process it at alater time or with off-line peripheral equipment.

In order to implement the invention while considering the restrainingfactors in the preceding paragraph, a method of analyzing the signaltransfer characteristics of a signal processing unit will now bedescribed in a slightly modified version than previously described, inthat advantage is taken of an information storage device which canretain information gathered quickly from the unit under test and whichcan be accessed later for information analysis. In effect, the methodinvolves establishing an input signal of known content, measuringselected parameters of selected parts of the input signal, storing theinput measurement results to define a sotred signature of the inputsignal comprising the selected parameters of selected parts of the inputsingal, feeding the input signal to the processing unit, measuring theparameters of parts of the output signal from the signal processing unitcorresponding to selected parts of the input signal, and subsequentlycomparing the parameters of the output signal with the correspondinginput signature parameters. When it is desirable to carry out the actualevaluation of the output signal measurements at a later time, the methodof analyzing just described can be supplemented by a further step in theevaluation process. That is, before comparing the output signal measurewith the stored selected input signature parameters, the measurements ofthe output signal can also be stored to define a stored signature of theoutput signal comprising selected parameters of selected parts of theoutput signal, and the comparing step would then comprise comparing thestored output signal signature with the stored input signal signature.Reference is made to FIGS. 3 and 4 and the following discussion for anunderstanding of this aspect of the invention.

As will be described later, the audio test tones applied during lead-inand lead-out of the tape or disc are preceded by a short burst of the6734 audio tone. It will be assumed that the audio recorded andretrieved from the recording medium will be at least two channels ofaudio, the test tones being applied to both channels in a selectivemanner, and the 6734 head tone being recorded and retrieved from onlyone channel (e.g., channel 2 of a two channel audio program). This headtone identifies the beginning of the audio test tone sequence, and theaudio on line 58 (FIG. 3) or line 58-2 (FIG. 4) from the audio and videoselector 53 is routed to the 6734 tone detector 41. The output of 6734detector 41 is routed over line 82 to the audio controller 21 whichprovides, under internal process control, all of the timing functionsfor the remainder of the audio test subsystem 5.

Audio controller 21 is enabled preparatory to the system recognizing the6734 tone burst by the operator, through keyboard 70, central controller1, and interface subsystem 3 by the sending of a request to the audiosubsystem to load its internal acquisition program and to activate theaudio test subsystem.

At the time audio test signals were generated and applied to the tape aSMPTE start code is entered by the tape operator to indicate the startof active program as expressed in hours and minutes. Similarly, a SMPTEend code as entered by the tape operator indicates the end of activeprogram as expressed in hours and minutes. Thus, upon command from theoperator to perform tape or disc evaluation, the central controller 1,via interface subsystem 3, enables the audio controller 21 in the audiotest subsystem 5 over line 18 with an "enable" signal.

The central controller then instructs the operator to rewind and startthe tape or disc from the beginning. The central controller sends theSMPTE start code minus 25 seconds to the interface subsystem 3 and loadsit into time code registers 116. In the same manner as previouslydescribed with depositing the test tone sequence to the pre-masteringtape, time code selector 51 alerts the audio controller 21 over line 76that lead-in of the tape of disc is being read. With the audiocontroller 21 now enabled, detection of the 6734 tone burst initiatesthe action of audio controller 21 to perform its timing sequences forthe various analyzing functions of the audio test subsystem over line30. One of the output control signals over line 30 is a control andtrigger signal routed to the multiprogrammer 23. Upon receipt of thecontrol and trigger signal, multiprogrammer 23 digitizes the segmentedaudio test tones on line 58, stores the digitized version of the testtones in memory, and under control of the audio controller 21, convertsa selected segment of the audio test tones to a continuous analogrepresentation and sends such representation over line 46 to audiosignal analyzer 25 for general analysis, and to audio spectrum analyzer27 for spectrum analysis of the lead-in and lead-out test tones. Directaudio on line 58 from the audio/video selector 53 is routed to an activeprogram spectrum analyzer 43 and a mono/non-mono signal check 62, theformer performing spectrum analysis of selected portions of the activeprogram material, and the latter making a determination as to whether ornot the two audio signals on the two audio channels of the playbackaudio are substantially the same or different, thereby indicating thatthe audio portion of the program is either monophonic or non-monophonic.The term "stereo" is not used in describing the function of the signalcheck block 62, since the invention is equally suited for analyzingaudio signals on the two channels in the form of monophonic,stereophonic, or totally separate audio tracks. An example of the needfor performing analysis on individual tracks totally separate from oneanother, i.e., the non-monophonic signal check, is that of a videoprogram in which the audio portion accompanying the video portion isbi-lingual, i.e., upon selection of either audio channel one or two, adifferent language can be selected to accompany the visual portion ofthe program.

The outputs of each of the signal analysis blocks of the audio testsubsystem are routed to a data evaluation subsystem 19 which, underinstructions from the operator through central controller 1 compares theaudio analysis results with standards, i.e., performs a signaturecomparison, and outputs the results of the evaluation onto a printer 15or visual display 17.

With specific reference to FIG. 3, the video from audio and videoselector 53 over line 118 is routed to the video test subsystem 7, thevideo signal being converted from analog to digital form by A/Dconverter 123, the digitized version being stored in digital memory 124and selectively processed or analyzed in video processor 125. The outputof video processor 125 is thus a video "signature" of the recoveredvideo signal, is outputted over line 126 to the data evaluationsubsystem 19, and the thus obtained output "signature" is compared witha stored signature in the data evaluation subsystem 19, the results ofwhich is printed on printer 15 and/or displayed at display station 17.

The time code or frame number selector 51 shown in FIG. 4 is thefunction block which compares frame code numbers from interfacesubsystem 3 generated by central controller 1 and ultimately from theoperating of the keyboard 70 by an operator, with either SMPTE timecodes or vertical interval time codes and output addresses identifyingthe lead-in audio test tone start frame, the lead-out audio test tonestart frame, both on line 28, and the program start and end frames online 76 and evaluate start frame on line 78. Audio controller 21 thusreceives an enabling signal from line 28 when the audio test tones areto be recorded or analyzed at the lead-in and lead-out locations, andthese frame positions on the recording medium are derived from decodingthe SMPTE time codes either on the cue data channel of the tape playeror audio channels of a tape or disc player. Similarly, the program startand end signals on line 76 and evaluate start on line 78, all from codeor frame number selector 51, enable audio controller 21 to initiate andperiodically check active audio as a result of decoding frame time codesfrom the vertical interval of the video received from the audio/videoselector 53 on line 118.

For purposes of illustration and to insure consistency of terminologyused in this specification with that normally used and accepted in theart, reference is made to FIG. 5 which shows a schematic representationof a length of video tape containing a lead-in portion, a lead-outportion, and a program material portion sandwiched therebetween.Assuming tape motion is to the right in FIG. 5, the beginning of thetape 55 has a lead-in portion 57, a test tone zone 59 on the lead-inportion, and a guard portion 65 of lead-in, all followed by the programmaterial portion 67. The test tone zone 59 on lead-in is comprised oftwo tracks of audio test tones, track 1 being represented by numeral 61and track 2 by numeral 63.

In symmetrical fashion, following the program material portion 67, alead-out guard portion 65 precedes test tone zone 59 comprised of audiotrack 1 shown at 61, audio track 2 shown at 63, and lead-out portion 57extending to the end of the tape.

The dotted line at 66 represents a control track for use insynchronizing the tape drive of the tape recorder upon playback, amongother things, and a cue track 68 upon which can be recorded a variety ofsignals, including time code frame numbers, editing data, additionalaudio, etc.

Although the tape configuration shown in FIG. 5 is known in the industryas the quad format, any of the other known formatting systems can beincorporated for use with the present invention, for example, theone-inch helical scan system or the 3/4-inch helical scan cassettesystem. The quad format represented in FIG. 5, however, will be referredto in the following discussions, and the cue track 68 will be what isreferred to hereinafter as data channel, the player output carrying thedata channel information identified as line 34.

Referring to FIG. 6, in order to have a known measurable set ofstandards upon which to qualify audio signals, a segmented signal trainof appropriate test signals is recorded on both the lead-in and lead-outareas of the pre-mastering tape. In a preferred embodiment of theinvention, audio test tones are recorded on both audio channels of thetape and occupy 12 vertical frame times in corresponding areas on bothof the audio channels as represented by the vertical dotted lines inFIG. 6. Preceding the 12 frames of test tones, on channel 2 a 6734 testtone location signal is applied immediately in front of the first frameon channel 2 in order to locate the test tone area when evaluating thetape or subsequently prepared disc copy.

The top half of FIG. 6 schematically shows the two audio channels 61 and63 with a literal designation of the type of signal contained in eachframe time period of each audio channel. The bottom half of FIG. 6 is adrawing of the approximate waveforms of the signals identified in theupper half of FIG. 6. During the analysis function of the audio testsubsystem, it should be noted that, although in normal play mode, theinformation contained in all 12 frames will occur in a time less thanone half second (12/30 sec. =0.4 sec.), the available test equipment isnot capable of performing complete measurements in such a short periodof time, and other processing of the signals is necessary in order tocarry out the measurement function. Briefly described earlier, and to bedescribed later in more detail, was a method and means for digitizingand storing the recovered analog test tones and converting them tocontinuous analog signals for analyzing at a later time.

In any event, when the contents of the first segment of the audio testtone train is analyzed, phase, amplitude, signal-to-noise, and harmonicdistortion measurements are taken. Since the two channels contain, forthe durations of segments 2 and 3, one kilohertz on one channelsimultaneously with DC (i.e., no signal) on the other channel, crosstalk measurements from one channel to the other are taken duringsegments 2 and 3.

During segments 4 and 7, each channel contains a DC level, and thusnoise level measurements are taken during these time slots.

A prescribed summation of 60 HZ and 7 KHZ tones is contained on segments5 and 6, and when analyzed with appropriate test equipment indicate theintermodulation distortion level through the recording and playbackprocess.

Finally, segments 8-12 contain audio tones continuously sweeping througha wide range of frequencies, i.e., from 20 HZ to 20 KHZ, and theanalysis of the recovered test tones in this area reflect the frequencyresponse of the transfer characteristics.

It should be noted that, in all of the analyzing of the pre-masteringtape or disc copies or of a throughput device, the "signature" duringtape evaluation or disc evaluation represents the personality, so tospeak, of the transfer characteristics either through the throughputdevice or through a recording/playback process, and the electronicsnecessary for recording and playback processing purposes are assumed tobe theoretically non-contributory to the "signature" or compensated forby appropriate pre-emphasis or pre-distortion techniques. This isespecially true in the recording/playback process in which theelectronics in the signal path are generally contributory to degradationof the signal in a minute or insignificant proportion as compared withthat attributed to the transducer components during the depositing andrecovering of signals from a magnetic tape or videodisc. Thus, for thepurposes of this invention, the contribution to the electronics involvedin the recording/playback process is considered negligible.

Turning now to FIG. 7, a schematic diagram is shown which produces theaudio test tones. A test tone generator and multiplexer 49 contains aplurality of function generators including a 6734 generator 73, a 1 KHZtone generator 75, a 60 HZ tone generator 77, a 7 KHZ tone generator 79,a sweep generator 81, and a DC source 83.

In the test tone recording process, upon command from the keyboardoperator, an enabling signal over line 18 is routed to audio controller21. The tape is rewound and put into play condition, whereupon the SMPTEcode derived by the central controller 1 is loaded into lead-in locationregister 87 and sent over line 86 to comparator 91. As the tape progressin its play mode, a position detector 85 reads the SMPTE time code offthe data channel tape recorder 11 and sends the detected positioninformation over line 84 also to comparator 91. After enabling of theaudio controller 21, the controller 21 interrogates comparator 91 fordetection of correspondence between the present position detected byposition detector 85 and the predetermined point at which lead-in testtone signals are to be applied, the latter location information takenfrom lead-in location register 87. When a comparison is found, an outputof the comparator 91 over line 28 initiates the subsequent multiplexingaction under control of audio controller 21. Basically, audio controller21, over line 72, selectively, and at a video vertical repetition rate,enables one or two of the function generators feeding multiplexer 71.Multiplexer 71 then sums the output of the selected function generators,and outputs the desired combinations shown in FIG. 6 over lines 76 and78 to be routed to the input channels 1 and 2 of tape recorder 11.

Simultaneously with detection of the compare signal on line 28, audiocontroller 21 outputs a record enable signal on line 80 to tape recorder11 in order to change the recorder from the play to the record mode sothat the audio test tones will be deposited, in the fashion shown inFIG. 6, on the separate audio channels.

Control of forward, reverse, play, and stop motions of the tape recorder11 are effectuated under control of audio controller 21 over the linesin cable 133. Not shown in FIG. 7 are communication links between thecentral controller 1, interface subsystem 3, and the audio testsubsystem 5 which communicate the operator's keyboard commands to theaudio controller for effectuating the various motion functions of thetape recorder 11. These are typical control communication paths whichcan be implemented in a variety of known ways.

FIG. 8 shows the audio test tone generation timing. In view of thelimited dimensions of a page of drawing, alpha/numeric codes areinserted in FIG. 8 to illustrate the contents of the segments of theaudio test tone train on each channel. The signal symbols shown in FIG.8 have the following correspondences:

T refers to the 6734 tone;

1K refers to the 1 KHZ test tone;

M represents the summation of the 60 HZ and 7 HZ test tones;

S represents the sweep function signal,

and a blank line represents a DC or zero signal component.

In FIG. 8, the beginning of the tape is at the left of the figure, andtrack 1 format waveform 90 has a lead-in portion 57 inclusive of lead-intones 61, 63, followed by a guard portion of lead-in 65, programmaterial 67, a lead-out guard band 65', and lead-out portion 57'including lead-out tones 61' and 63'.

The data channel output shown schematically in the third line of FIG. 8represents at each vertical marking the SMPTE position code data at avertical frame rate. Position A indicates the SMPTE time code which issufficiently upstream of the program material (generally 25 seconds ormore) and the position at which recording of the audio test tones is tobegin. The first position, position A, is that of the 6734 tone followedby the actual test signals referred to in FIG. 6. The position A SMPTEcode having been detected by position detector 85 and compared with thestart position location at comparator 91, audio controller 21 enablesthe tape recorded over line 80 with a waveform shown in the fourth lineof FIG. 8. The record mode shown as record enable waveform 93 indicatesthat tape recorder 11 is placed in the record mode during the positiveduration of the record mode waveform. Since the test tones require lessthan a half second of time, the guard bands 65 and 65' are still on theorder of 241/2 seconds, providing a safety factor so as to avoid anyinadvertent erasing of the program material on the extreme ends of thetape.

The third line of FIG. 8 also shows, at position B, the coincidence oflead-out SMPTE location number stored in location register 89 andcompared with the present position from position detector 85 atcomparator 91.

A similar recording procedure is then effectuated under audio controller21 control by enabling the record mode of tape recorder 11 over line 80at the time position B code is detected. The resultant pre-masteringtape thus contains the 12 segment audio test tone train at both lead-inand lead-out segments of the tape, and this location of test tone datawill be carried through the disc mastering, replication, and playbackprocesses so that audio analysis of either the tape or disc can be madein the manner briefly described earlier in this description.

A general block diagram of the audio analysis logic is shown in FIG. 9.In the manner described in connection with FIG. 3, both a disc player 9and a tape recorder/player 11 are shown connected to an audio selector53 (the audio portion of audio and video selector 53) the two audiooutputs of disc player 9 being carried by line 32, while the twochannels out of the tape player 11 are carried by line 16. Channels 1and 2 audio out of the audio selector 53 are carried on lines 58-1(channel 1) and 58-2 (channel 2). It will be noted that only channel 2audio is sent to the 6734 detector 41, consistent with the waveformsshown in FIG. 6. The audio on line 58-1 enters A/D converter 37, isdigitized thereby and sent over line 36 to the digitized test tonesmemory 33 for storage. Under command of the audio controller 21, acontrol and trigger signal on line 30 is effective to cause recirculatecontrol 99-1 to recirculate a selected test tone segment in thedigitized memory 33 and output that selected tone segment in acontinuous manner over line 38 to D/A converter 39. The continuousrepresentation of the selected test tone is then routed over line 46 tothe audio signal analyzer 25 and lead-in/lead-out spectrum analyzer 27as described briefly earlier. The outputs of the two analyzers 25 and 27are routed over lines 48 and 50 to audio analysis memory 47. The memoryunit 45 thereof has information written into it by memory write gates 44which receive outputs from multiplexer 42 in a timed manner undercontrol of audio controller 21 over line 30. Thus, all inputs to themultiplexer 42 are sequentially acted upon to be stored in memory unit45 for later evaluation by the evaluation subsystem.

The analysis of the appropriate locations during lead-in and lead-outfor recovering audio test tones to be analyzed in controlled byoutputting a signal on line 28 from comparator 91 when the appropriateframe numbers during lead-in and lead-out have been detected. Whetherthe audio test subsystem is analyzing the tape or the disc, presentposition data is received over lines 34 and 118, respectively, byposition detector 85. The present position is then routed over line 84to comparators 95 and 91. Comparators 95 and 91 operate in similarmanners, i.e., a desired tape or disc position is contained in locationregisters, and the contents of such registers is compared with thepresent position data to enable the audio controller 21 at coincidencethereof. In FIG. 9, the two comparators 91 and 95 are shown separately,since they perform slightly different functions in carrying out theaudio analyses.

That is, comparator 95 makes a comparison of the time code contained inthe video information of the active program material so as to identifyprogram start, program end, and various points along the programmaterial content at which active audio and/or video tests are to becarried out. On the other hand, since there is no video contained in thelead-in and lead-out portions of a tape or disc, comparator 91 must relyupon SMPTE time code detection from either the data channel out or audioout signals of the tape and disc player.

After lead-in analysis has been accomplished, the audio test subsystemproceeds to analyze active audio program material at predetermined timeintervals during the active programming. Comparator 95 is thus providedwith present position data from the vertical interval of the videosignal, and location register 109, when matched with present position,outputs a program start signal to the audio controller 21 to ready theaudio controller for subsequent active program analysis control. At thefirst predetermined location in the active program wherein audio is tobe analyzed, location register 111 will have a position location matchwith present position from position detector 85, and comparator 95 willoutput an evaluate start signal over line 78 to audio controller 21.Control then of two additional audio analysis functions of the audiotest subsystem commences under control of audio controller 21 over thecontrol line generally designated at 30 in FIG. 9.

The audio from both channels of the playback device exiting audioselector 53 enters active program two channel spectrum analyzer 43.Analyzer 43 contains two analyzer arrays, one for each of the audiochannels. Since the audio to be analyzed during active program materialis continuous, it is not necessary to digitize and recirculate audiosegments in the multiprogrammer 23 as was necessary with the shortsegment deration test tones of the lead-in and lead-out portions of thetape or disc. Accordingly, the audio entering spectrum analyzer 43 isselected audio direct from the playback devices. Both arrays 113 and 115of the spectrum analyzer 43 operates in identical fashion, i.e., a 45second audio waveform from each audio channel is acquired andtransformed into two frequency spectrum of 128 separate frequency pointsfor each channel. Point spacing is in 200 HZ increments, and each valueanalyzed at each point is expressed in decibels. The frequency spectrumfor each sample represents a unique audio "print", and the 128 pointsfor each channel have their values contained on lines 56 and 60,respectively, and these values are multiplexed with the other analyzersignals in multiplexer 42, and ultimately stored in memory unit 45. Aswas suggested earlier and discussed in detail later in this description,the evaluation of all of the analyzing signals comprise a part of thesignature for both the tape and the disc signal outputs, and thus in thefinal printed report of the evaluation, and using the frequency spectrumanalysis as an example, represents the results of subtracting each pointin the disc frequency spectrum from the corresponding point in the tapefrequency spectrum. An analogy can be gathered from this as regardsother "prints" obtained from the individual analyses of the audio andvideo signals which comprise the ultimate "signature" established duringtape evaluation and disc evaluation.

Another part of the "signature", and therefore another input tomultiplexer 42, is a signal on line 54 indicating whether or not theaudio portion of the program is monophonic or non-monophonic. The signalis developed in the mono/non-mono signal check block 62. Channel 1 andchannel 2 audio are received by block 62 over lines 58-1 and 58-2,respectively, these two signals being compared with each other inamplitude comparator 105. Mono/non-mono testing is performed atintervals throughout the active programs areas of the tape or disc. Eachtest consists of 65,536 measurements, the measurements being spaced onemillisecond apart.

Block 62 illustrates a preferred embodiment of the mono/non-mono checkin which the amplitudes of the two audio channels are continuouslycompared in comparator 105 with the difference between the two audiochannels being outputed on line 84. If the amplitudes are within 5% ofeach other, threshold detector 107 does not react to the signal on line84, there is no output on line 86, and a 1 KHZ clock 103 is applied overline 88 to the mono/non-mono counter 101. Without an input on line 86,i.e. the amplitudes of the audio on both audio channels are within 5% ofone another, counter 101 is incremented by 1 count. One millisecondlater, as determined by the pulse recurrent rate of 1 KHZ clock 103,counter 101 is again incremented if the amplitudes are again within 5%of one another. This procedure continues in like manner until themeasured amplitudes between the two audio channels are greater than 5%in difference, at which time threshold detector 107 outputs a stepwaveform on line 86 to inhibit counter 101 from incrementing one count.As a result, after counter 101 permits 65,536 clock pulses to incrementor not increment the counter, the accumulated count is sent over line 54to multiplexer 42 and stored in memory unit 45 by memory write gate 44to become a part of the "signature" for the unit tested.

Obviously, in the printout of the analysis performed by the audio testsubsystem, the greater the number count on line 54, i.e. the closer theaccumulated count is to 65,536, the more definite it is that the twoaudio signals on the two audio channels are the same, i.e. the audioprogram is monophonic. An accumulated number count in the "signature" of30,000 to 50,000 would indicate that the audio program is likelysterophonic, the greater the stereo separation on the two channels, thelower the number count will be. Finally, an accumulated number count of30,000 or below would indicate the likelyhood that the programs on thetwo channels are entirely different audio programs, for example abi-lingual program in which each channel has its own peculiar languageversion of the audio portion of the program.

An alternate implementation of the mono/non-mono check block 62 isrepresented by the dotted line 88' from 1 KHZ clock 103 to amplitudecomparator 105. In this embodiment, the amplitude of the audio on thetwo channels 58-1 and 58-2 are not compared continuously, but rather arecompared under the gating action of the 1 KHZ clock, that is, acomparison is made every millisecond. Comparator 105 is then arrangedsuch that, when the amplitudes of the signals of the two audio inputlines 58-1 and 58-2 are within 5% of one another, an output pulse isrouted to threshold detector 107 long line 84. The output of thresholddetector 107 is then a step when the amplitudes on the two audiochannels are within 5% of one another and DC when the amplitudes aregreater than 5% of one another. Since comparator 105 is clocked at a 1KHZ rate, the maximum frequency step signal out of threshold detector107 is also 1 KHZ, and when a stereophonic or non-monophonic program isbeing and counter 101 is incremented fewer times. Again, assuming thatamplitude comparisons are made in comparator 105 65,536 times, thisembodiment of the mono/non-mon signal check merely counts the number oftimes that the amplitudes of the samples from the two audio channels arewithin a prescribed percentage tolerance of one another (5%) to provideinformation regarding whether or not the signals on the two channels aresubstantially similiar in informational content.

FIG. 10 is a more detailed diagram of the audio controller 21, showingthat it is basically comprised of a processor 29 and read-only memory31. Read-only memory 31 can take on any of various forms of memory suchas tape cassette, hard wired or burned in micro chips, and the like. Thepurpose of the memory is to set up the control functions of the audiocontroller in a prescribed manner upon enablement by the centralcontroller 1 and/or interface subsystem and line 18, the processorinstructs the read-only memory 31 to prepare the processor 29 foroutputting its control logic on line 30 (representing a plurality ofactual signal lines) depending upon subsequent signals received byprocessor 29. The functions of the program start, evaluate start, starttones signal, and lead-in/lead-out "match" signals have been explainedearlier. In this connection, although a single line 30 is shown as"control out" in FIG. 10, it can be appreciated that, due to the numberof items in FIG. 9 with which the audio controller must communicate,line 30 is merely representative of a cable containing multiple controllines, as necessary, to control the various functional blocks of FIG. 9.

In FIG. 11, there is shown, in more detail than before, signal routingassociated with the audio and video selector 53 and time code or framenumber selector 51. Since the AVQMS is capable of analyzing and creatinga "signature" for a tape program or disc program, in the interest ofeconomy and efficiency and without loss of quality, the audio outputsfrom the two channels of the disc player are shown entering audio andvideo selector 53 on lines 32, while the comparable outputs from thetape player are shown on lines 16. Under operator control, audio andvideo selector 53 outputs the active audio portion of the program online 58-1 and 58-2. It will be recalled that only channel 2 audio isrouted to the 6734 tone detector 41, since that tone is only depositedon channel 2. A "start tones" signal is thus produced by detector 41 online 82 as discussed in connection with FIGS. 9 and 10.

The lead-in and lead-out identification signal, herein referred to asthe 6734 tone or code signal, can, in a simplified system be comprisedof a non-standard frequency such as 6734 HZ lasting the time of onepicture frame preceding the sequence of test tones in the lead-in andlead-out portions of the tape or disc. However, a better identificationsignal is preferably a coded form for a sequence of numerical digitssuch as 6, 7, 3, and 4. The code is a self-clocking digitalrepresentation of the number series 6734 which is chosen so as to removefrom chance (for all practical purposes) the possibility that any otherrandomly recovered signal from tape or disc would falsely appear to bethe identification signal. The coded digits are represented in binary byswitching between two square wave source tones, a 1 KHZ tone and a 2.5KHZ tone, according to 1 and 0 binary states, respectively. Upondetection by 6734 detector 41, the transitions attributed to the 1 KHZtone are interpreted as logical 1's, while the transitions attributed tothe 2.5 KHZ tone are interpreted as logical 0's. Upon detection of aproper combination of 1's and 0's making up the binary representationsof 6, 7, 3, and 4, detector 41 outputs a "match" signal to indicate thatthe series of lead-in and lead-out test singals follow.

The encoding techniques briefly described above, are described ingreater detail in a previously filed application Ser. No. 68,530 filedAug. 22, 1979, entitled "PROGRAMMED VIDEO RECORD DISC AND RELATEDPLAYBACK APPARATUS", now abandoned in favor of a continuation Ser. No.210,921 filed Nov. 28, 1980, now abandoned in favor of a continuation,Ser. No. 407,003, filed Aug. 10, 1982; all commonly owned herewith.

Although the discussion so far has involved processing, analyzing, andevaluating audio program material, video signals are utilized in theaudio test subsystem for the purpose of determining when active audio isto be analyzed, and such information is derived from the frame numbercodes in the verticle interval of the video signal. Accordingly, thevideo from disc player on line 147 and the video from tape player online 149 are routed to selector 53, and depending upon which program isto be analyzed, disc or tape, an output video signal on line 118 isrouted to frame number selector 51. When the predetermined frame codefrom the interface subsystem on line 18-2 is compared with the videoframe number code in selector 51, a "program start" signal is generatedon line 76 upon coincidence of the first frame of the active videoprogram with the predetermined frame code number, and subsequently an"evaluate start" signal is generated on line 78 upon coincidence of thepredetermined points of analyzing the active audio portion of theprogram with predetermined frame codes. Since audio analyzing isaccomplished in a rather short period of time as compared with thelength of most programs (e.g. 45 seconds for spectrum analysis and 65.5seconds for mono/non-mono check), a number of predetermined frame codeson line 18-2 received by selector 51 will result in a plurality ofspaced "evaluate start" signals on line 78.

As explained earlier, since the lead-in and lead-out portions of theprogram do not contain video information, the data channel output of thetape player on line 34 or, alternatively audio containing SMPTE codefrom the disc player is routed to selector 51 and compared with theappropriate frame code (in SMPTE code) to output a "match" signal online 28 to initiate either recording or retreiving the train of audiotest signal segments of the lead-in and lead-out test signals.

Details of the multiprogrammer 23 is shown in FIG. 12. The purpose ofthe multiprogrammer 23 is to receive audio in on line 58 from thelead-in and lead-out portion of the program and to output a continuousversion of the audio on line 46. Additionally, multiprogrammer receivesa control and trigger on line 30 for synchronizing the inner workings ofthe multiprogrammer, and outputs a 1 KHZ clock as the one millisecondtiming signal for mono/non-mono signal check 62.

The segmented audio test signal train is received on line 58 andconverted to digital form by A/D converter 37. Upon sensing the 6734tone in detector 41, audio controller 21 sends control and triggersignals along line 30 to the program storage 35, A/D converter 37, andtimer pacer 103.

Control to program storage 35 merely resets the internal program of themultiprogrammer so as to acquire, recirculate, and output audio at theappropriate times. The trigger on line 30 to pulser 97 and pacer 103 isgenerated upon detection of the 6734 start tone. Typically, pulser 97outputs a 32 KHZ square wave for activation of the A/D converter 37,while pacer 103 outputs a 64 KHZ square wave for digital-to-analogconversion timing in D/A converter 39. The 1 KHZ clock output on line88a is the basic timing source for the mono/non-mono check block 62. Inthis connection, the 1 KHZ clock circuit 103 in FIG. 9 shapes the clockfor distribution within the mono/non-mono check block 62.

With the digitizing pulses configured as described above, A/D converter37 converts the real-time audio in on line 58 and stores it inacquisition storage 33. It should be recalled that, subsequent to the6734 start tone, twelve segments of audio test tones are received bymultiprogrammer 23, and at a 30 frame per second rate, all twelve frameswill be written into acquisition storage 33 in 0.4 seconds.

In order to analyze a continuous form of each segment of the audio testtrain in lead-in and lead-out, program storage 35, under control ofaudio controller 21, retreives, in turn, each selected segment of theaudio test tone train, recirculates it via control of recirculatecontrol 99 over line 80, and causes a continuous form of the particularselected segment to be outputted over line 38. D/A converter 39, timedby pacer 103, then outputs a continuous analog version of the selectedaudio test tone segment over line 46 for analyzing by the signalanalyzer 25 and spectrum analyzer 27 shown in FIGS. 4 and 9.

The functioning of the audio test subsystem has been described in termsof signal routing between circuit blocks of the foregoing figures. FIG.13 should serve to clarify the signal routing details and provide atiming analysis of the many signals described only verbally heretofore.The audio waveform of channel 1 is shown schematically at 90 in FIG. 13,while the channel 2 waveform is shown at 92. The beginning of the tapeor disc is to the left in FIG. 13. Both channels 1 and 2 show the testtones in lead-in, followed by program material, followed by lead-outtest tones.

Since only lead-in and lead-out test tones are acquired from therecording medium of a rate too fast for analyzing, only these testsignals need to be digitized, stored, and recalled for further analysisat a later time. Accordingly, digitized audio waveform 94 indicates thatmultiprogrammer 23 is performing its digitizing under control of audiocontroller 21 only during lead-in and lead-out time. As explainedearlier, analysis of the program material is accomplished in real-timeand needs no digitizing technique applied.

"Program start" waveform 96 occurs as a single pulse at the beginning ofthe program material. As explained earlier, this pulse is sent to theaudio controller 21 to clear and reset the internal audio processerpreparatory to taking active audio samples for analysis.

On the other hand, "evaluate start" waveform 98, occurs periodicallythroughout the program material and is shown by way of example in FIG.13 as occurring four times. Since the longest active analyzing time isapproximately 65.5 seconds, it is obvious that "evaluate start" pulsescould occur at a corresponding or slightly lower rate. Depending uponthe confidence level in the analysis results, the extent of desired discor tape evaluation consistent with available hardware and timerestraints, and the relative importance of each particular parameteranalyzed, evaluation of the active program material can be varied byadjusting the pulse repetition rate of the evaluate start signal inorder to optimize the above-mentioned parameters.

In any event, FIG. 13 shows an "evaluate start" pulse at the beginningof program material, and as a result, the count from counter 101 (FIG.9) begins to be accumulated. Waveform 100a shows a plurality of countsoccurring at a 1 KHZ rate, and assuming that a theoretical monophonicsignal has been recorded in both audio channels 1 and 2, most, or all ofthe 65,536 samplings are shown to exist, thereby indicating the presenceof a monophonic program on the two audio channels. On the other hand,waveform 100b illustrates the effect of acquiring and analyzing anon-monophonic audio program on the two channels, and only occasional 1KHZ pulses are present to be accumulated, and the scarcity of counterpulses will accumulate, after 65.536 seconds, to a small numberindicating the existence of a non-monophonic program on the two audiochannels. It should be appreciated that, due to spacial limitations, thepulses indicated at 102a and 102b of waveforms 100a and 100b,respectively, are only schematic representations of the actual waveformswhen viewed on an oscilloscope.

Audio controller 21, over line 80, creates waveform 104 having "saveaccumulated count and clear counter" pulses 106 applied to mono/non-monocounter 101 so as to output the accumulated count over line 54 to beanalyzed by audio analysis memory 47, having reference again to FIG. 9.

In a similiar manner, audio controller 21 creates the approximate 45second enabling pulse 110 of waveform 108 to activate the spectrumanalyzer 43, and during the relaxation time after the 45 second analysispulse 110, a pulse 114 shown on waveform 112 is effective to causespectrum analyzer 43 to output the test results from the spectrumanalyzer, such results being referred to "spectral print" to become apart of the signature after evaluation.

Shown in FIG. 14 is the video test subsystem. The video subsystem 7comprises essentially two logical units, an acquisition unit 119 and aprocessing unit 125. Acquisition unit 119 has the capability to acquirea video signal in a controlled manner, convert it from analog signal todigital values in A/D converter 123 and store a digitized signal inacquisition digital memory 124 over line 130. Typically, digital memory124 has 32K bytes of acquisition memory, and an analog-to-digitalconversion results in an 8 bit byte. One of the 525 lines in a frame isrepresented by 910 conversions or bytes, converted in real-time, eachEach picture horizontal line being 63.5 microseconds in duration. Thevideo test signals are encoded during vertical intervals in lines 19 and20, and under program control of processing unit 125, selected lines orportions of lines from a frame or from consecutive frames may beconverted and stored until the 32K bytes of acquisition storage isfilled.

Control of the acquistion unit 119 and computation of the acquired datais performed by processing unit 125. The processing unit 125 features amicroprocessor computer 120, processing storage 121, and a real-timeclock 122. Having acquired and stored the selected video test signals,control of processing unit 125 is effected by a control line 135 frominterface subsystem 3. In a manner of control analogous to thatassociated with the audio test subsystem discussed earlier,microprocessor computer 120 accesses over line 128 the digitized andstored video test signal from digital memory 124 over line 127. Timebased from real-time clock 122 over line 129, computer 120 andprocessing storage 121 interplay to output over line 126 the analogequivalent of the video test signal or portion thereof being processedand route same to the data evaluation subsystem to become a part of the"signature" of the tape or disc being evaluated.

While the concepts underlying this invention apply equally well to allworld standard television systems and format, the numerical values andtiming parameters given in this specification make reference, as exampleonly, to the NTSC system. FIG. 15 is a diagram showing two consecutivehorizontal lines comprising a color frame according to the NTSC system.Field 1 is shown by arrow 170 defining the horizontal interval H at 174,with the vertical interval shown at 176. Field 2, shown at arrow 172shows the odd field with the vertical interval preceded by 0.5H andvertical synch pulse 178. For conservation of space in the drawing,horizontal lines 11-18 are omitted in the drawing, and lines 19 and 20preceding the recurrence of the video picture information in a standardNTSC video signal are made available to contain the aforementioned videotest signals. A composite VITS test signal, shown in FIG. 16, is locatedin each frame in field 1, line 20 and with appropriate measuring devicescan provide some 15 measurements of different video parameters.

A combination VITS video test signal is located on each frame in field2, line 20 and provides some 11 measurable parameters.

Finally, a VIRS test signal as shown in FIG. 18 is located in each framein both vertical fields on line 19 to provide some 9 additionalmeasurable parameters. Available video test equipment can be used tomeasure substantially all of the VITS and VIRS test signals.

In FIG. 16, the color burst is indicated at 180, the white line bar isshown at 181, a T-step transition 182 follows the line bar 181, a 2 Tpulse 183 follows the T-step 182, and a stair step or modulatedstaircase 184 fills the remainder of the horizontal line of information.

Similiarly, and with reference to FIG. 17, a white flag 186 is followedby a series of 6 bursts of increasing frequency test signals, known asmultiburst, burst 187 being at 5 KHZ, burst 188 at 1.0 MHZ, burst 189being at 2.0 MHZ, burst 190 being at 3.0 MHZ, burst 191 being at 3.58MHZ (color burst frequency) and burst 192 being at 4.2 MHZ. A threelevel crominance test signal 193 follows the multiburst and fills theremainder of the horizontal line of test signal.

In FIG. 18, the VIRS test signal has a phase correcting color burst 195,followed by luminance levels 196 and 197.

The specifications for time period, amplitudes, and rise and fall timesshown in FIG. 19 represent NTSC standards for the horizontal blankingand sync pulse with color burst. The specifications given in FIG. 19,when taken together with those shown in FIG. 15 comprise many of theparameters which are to be tested for compliance with NTSC standards. Itis common for broadcast companies to have an on-line test system forverifying that the program sent over the airwaves meets acceptable NTSCstandards, and this is generally done on a continuous basis. An exampleof a piece of equipment which is capable of measuring the parametersheretofore referred to is the Tektronix Model 1980 automatic videomeasurement set. The waveform examples shown in FIGS. 15-19 are thusknown standardized waveforms which can be fully evaluated and verifiedfor compliance with NTSC standards by the Model 1980 Tektronixapparatus, and the descriptive and illustrative information contained inthis application regarding the particular video test signals andspecific parameters tested are presented to indicate the kind of testingwhich is typically carried out by those skilled in the art. It is to berecognized, however, that the basis for the subject invention has to dowith the manner in which the test data is gathered, processed, and usedin an evaluation processing scheme. The previous discussions concern thetesting of a video tape or video disc signal, comparing it with fixedstandard deviation limits, and establishing from the test dataacceptable tolerance limitations for each of a variety of parameters soas to form a "signature" against which test results of subsequenttesting of other tapes, discs, or copies can be compared. Thus, it isgenerally not within the scope of this application to discuss theprecise manner in which all of the video test parameters are analyzed,but rather in the manner in which the test information is gathered,processed, and evaluated.

An exception lies in the noise test which is generally carried outduring vertical interval times of a broadcast program. That is, a noiseamplitude measurement is made on a theoretically flat portion of thevideo waveform, during vertical interval. The noise can be expressed interms of amplitude, IRE units, a percentage of maximum peak-to-peaksignal amplitude, or in decibels as compared with a fixed amplitudelevel of the video signal. A standard test procedure for evaluatingnoise levels is to measure the peak-to-peak amplitude of the noisedeviation during the horizontal sync pulse which is theoretically to beat a DC level for approximately 4 microseconds. The noise test can betaken during the horizontal sync pulse duration at any of a number ofgiven lines during vertical interval. For example, the noise test can betaken on any of the horizontal sync pulses of lines 10-21 of thewaveform in FIG. 15. It could also be taken during the lower transitionportion of the vertical sync pulse 176 or 178. Broadcast signals, andeven signals from tape reproduced programs have rather randomly producedsignal deviations as compared with acceptable standards. In a broadcastsituation, a tolerance might be exceeded by the aging or degradation inquality of a component part of the electronics through which the signalpasses. In a video tape situation, a defect or blemish on the tape wouldproduce an out-of-tolerance condition at the moment the tape defect isbeing scanned by the read head, but the next and subsequent defects willlikely occur in random fashion, since there is no correlation betweenphysical placement of the recorded program on the tape and therepetition rate of any tape defect. On a video disc, however, andespecially on one which uses a constant angular velocity (CAV) format,if the noise test was taken only during vertical interval, only a smallpercentage of the disc's surface area would be contributory to the noisemeasurement. This is illustrated in FIG. 21 which shows, schematically,the two vertical interval V-shaped portions 207, and assuming the discrotates in a counterclockwise direction, the dotted line 208 representsthe position at which noise tests would normally be taken, i.e., on agiven horizontal sync tip at a given line number of each verticalinterval. Even if such a noise test were taken during each verticalinterval between alternate fields, it can be appreciated by reference toFIG. 21 that only a very slim localized area of the disc would beevaluated by the noise test. Accordingly, and consistent with one of theobjects of the present invention to perform evaluation tests on videodiscs, the noise test according to the present invention is taken oneach horizontal blanking pulse of any desirable portion of videoprogram. As shown in FIG. 20, the back porch 201 of the horizontalblanking pulse following the color burst 180 has a theoretically flatshape during the time indicated by arrow 202. According to the presentinvention, a noise evaluation is made during the time indicated by arrow202, and since this is accomplished on each horizontal blanking pulse,substantially the entire area of the disc can be tested for noiseproblems, and this is shown in FIG. 21 wherein, rather than the radialline of evaluation shown at 208, noise figures are taken from the discat each of the dash lines 209. Although only two rows of dash lines 209are shown represented in FIG. 21, it can be appreciated that each ofsome 54,000 circles of dashed lines 209 would show on a full scaledrawing, and therefore it can be appreciated that any blemishes on adisc outside the vertical interval will be taken into account in thenoise measurement. This represents a substantial improvement invideodisc quality assurance as compared with the normal noise teststaken only on a single horizontal sync tip 200 as seen in FIG. 20, andthen only during vertical interval occurrences.

A block diagram of the circuitry used for effectuating the unique noisetest according to the aforedescribed procedure is shown in FIG. 21B.FIG. 21B should be analyzed with a view to FIG. 14 wherein like numbersrepresent like functional blocks of the two diagrams. In the noise testarrangement of FIG. 21B, video in over line 118 is digitized inanalog/digital converter 123 and advanced to a sample and hold circuit137. Sample and hold circuit 137 makes eight samples of the waveformportion 202, shown in FIG. 20, and stores the results in digital memory124. The processing of the noise test data is accomplished in separatefields of the video signal. It should also be noted that, since it isnecessary for the sampling of the circuit 137 to sample identical partsof adjacent horizontal blanking signals, only the horizontal blankingsignals outside the vertical interval are noise tested. Accordingly,typically about 480 lines per frame are sampled for the noise testmeasurement.

The video of field 1 is routed to mean detector 139-1 which calculatesthe mean value for the eight samples, and the variance detector 141-1outputs the variance from the mean, such variance being forwarded to theaveraging circuit 152. In like manner, the sampled noise of field 2 isrouted to mean detector 139-2, the variance from the mean thereof beingdetected by variance detector 141-2, and the results also sent toaveraging circuit 152. The average of the two noise figures are thusoutputted on line 126 as measurement data out, and such measurement datais sent to the data evaluation subsystem to be discussed later.

With reference to FIG. 22, the video analysis logic is shown. Becausethe testing of different sources of video program material requiredifferent control of the sample points for making measurements, a memory138 is provided to contain a list of frames to be measured. Uponreceiving an "enable" signal from interface subsystem 3, controller 142initiates forward, reverse, stop, and play functions of the disc player9 or tape player 11 to ultimately cause one of these devices to outputits video information over lines 147 and 149, respectively, to videoselector 53. In the meantime, controller 142 clears over line 161counter 140, and the first frame number to be measured is outputted frommemory 138 over line 169 to comparator 136. When the video on line 118out of video selector 53 is decoded as to frame number by frame decoder134, a comparison in comparator 136 is made, and a "take measurement"signal on line 157 is routed to controller 142. Controller 142 theninitiates the testing of the video test subsystem 7 by outputting an"enable" signal on line 175. Simultaneously, controller 142 enablesmemory write gates 144 so that the video test data on line 126 out ofvideo test subsystem 7 can be stored over lines 167 into video analysismemory 146. The position in memory 146 to which each test analysissignal is to be written is controlled by address bus 165 havingcoincidence with the frame number under test.

Upon conclusion of memory storage for one sampling of video test signal,the second in the list of frames to be measured is outputted from memory138 over line 169, and another comparison is made in comparator 136 withpresent frame number in order to again instruct controller 142 to "takemeasurement" over line 157. Controller 142 uninhibits memory gates 144to gain write the new test data analysis in memory 146 at the addressfrom counter 140 over address bus 165. Again, controller 142 incrementsover line 163 counter 140 so that the next frame number to be measuredis read out of memory 138.

This process continues until all of the test samples have been taken foranalysis by video test subsystem 7 and written into memory 146. Theoutput of memory 146, as discussed earlier, is routed over line 126 tothe evaluation subsystem.

FIG. 23 shows a block diagram of the audio/video data evaluationsubsystem. As explained in connection with FIGS. 3, 4, 9, 14, and 21B,all of the audio and video analysis data from either tape, disc, orthroughput device, is sent to the data evaluation subsystem. Prior toprocessing in the evaluation subsystem 19, the analytical processing bythe electronics has been referred to supra as "analysis". In thisspecification, the term "evaluation" has the special meaning ofprocessing the "analysis" information in such a manner so as to"evaluate" the unit under test, and in a specific practical applicationof the invention, such evaluation is tantamount to a pass or failstatement for the unit under test.

Although throughput devices have been described earlier as beingevaluatable using the concepts of this invention, FIG. 23 shows thetypical evaluation of audio and video from a copy of a master program. Ablock numbered 211 represents the audio analysis data from the mastersource of program material, while block 212 represents the analysis ofcorresponding data from the copy made from the master. Similarly, mastervideo analysis is represented by block 213, while corresponding videoanalysis of the copy is represented by block 214. An audio comparator215 compares the master and copy analysis data, and the differences arerouted to a printer 15 to enable visual and permanent storage of thelist of differences. Similarly, video comparator 216 processes thedifferences in video analysis between master and copy and prints theresults in the list of differences. As will be seen in subsequentfigures, the audio and video comparators 215 and 216 do more than makemere line-for-line comparisons of the signals from master and copy, butrather involve the unique concept of comparing "signatures" ashereinbefore defined.

FIGS. 24-27 illustrate different "evaluation" schemes utilizing theconcepts of the present invention. The first of these figures, FIG. 24,"tape evaluation", shows that a video tape 154 is prepared by recordingon program tape recorder 145 the picture and/or sound from a programsource 143. Generally, the picture and sound program source is that of acustomer's master video tape or a motion picture film. In either case,tape 154 is prepared from the customer's tape or film program source forthe purposes of using tape 154 as a pre-mastering tape for eventual usein preparing the disc master. At the time the program is recorded ontape 154 by recorder 155, appropriate video test signals from testsignal generator 148 are recorded during the vertical interval portionsof the program. In preparing the pre-mastering tape 154, sufficient timeis left before the program material and after the program material onthe tape so as to allow for insertion of the lead-in and lead-out audiotest tones. Thus, at the time the program is recorded on thepre-mastering tape 154, or at a later time, as desired, audio test tonesare recorded on tape recorder 150 (or tape recorder 145 if desired), andthe resulting tape 154 now contains lead-in test tones, programmaterial, and lead-out test tones.

A player 156 outputs the audio and video signals to their respectiveanalyzer 158, and the characteristics of the test parameters measured byanalyzer 158 form parameter list 154 which can take the form of a visualdisplay or hard copy readout. At this point, other than the applicationof audio test tones during lead-in and lead-out, "tape analyzing" hasbeen accomplished, and the character of the tape is reflected in theanalysis of the tested parameters listed in parameter list 164, and thistype of analyzing is not uncommon in the tape manufacturing field. Thepresent invention, however, goes beyond mere analysis of a signal sourcein that, from the parameter list 164, parameter deviation limits areset, either manually or under computer control by limits setter 166. Therange of parameter deviations permitted by limits setter 166 can beestablished by applying a percentage figure to the measured parameter ofthe parameter list 164 and storing the deviation limits so derived in asignature store 168. Desirably, prior to the listing of the parameteranalyzed in parameter list 164, a fixed standards table 162 is used as acommon (e.g. NTSC, PAL, or SECAM) standard for comparing the output ofthe analyzer 158 in comparator 160. For example, where the FederalCommunications Commission, SMPTE, EIA, or other standards group hasestablished precise parameter tolerance limitations on audio and videosignals, comparator 160 ensures that the parameters listed in parameterlist 164 are within such industry standards. On the other hand, limitssetter 166 is more in line with acceptable limits permitted by theparticular process involved in a particular manufacturer's recordingprocess. Thus, when a copy is made of pre-mastering tape 154,corresponding signals from master and copy are analyzed in analyzer 158and evaluated in evaluator 171 by comparing the signature in signaturestore 168 with the output of analyzer 158. The quality of the copy isthus compared against essentially two standards, the industry acceptedstandards according to standards table 162, and an internalmanufacturer's standards set by limits setter 166. As a result, thesignal evaluated by evaluator 171 is not merely weighted against fixedindustry standards as has been done in the past, but is rather comparedagainst a "signature" which is representative of the character of therecording process which should be repeatable within certain limitations.In this way, the degradation of the copying process can be evaluatedagainst a more realistic reference, i.e., against a previously recordedsignal using the same kind of tape, same recorder, and same signalsource so that these latter items can be nullified as to theircontributory effects.

As compared with analyzing processes which evaluate a recovered tapesignal against fixed, often calculated, standards, evaluating a copy, orsimilar recorded program, against a "signature" permits the manufacturerto pinpoint smaller out-of-tolerance deviations and thus allow isolationof the problem areas of a process so that corrective action can betaken. Similarly, comparing against a "signature" characteristic canshow the degrading effect of a process even when the signal retrievedfrom the second and subsequent recordings are within tolerances ascompared to fixed standards. In other words, it is conceivable that fora particular recording process, the test results of analyzing aparticular parameter is within extremely tight limits and of moreoptimum value than industry standards requires. As a result, thesignature will reflect an unusually high standard for that particularparameter. This is a result of setting the limits on the basis of priortest results and not industry standards. Thus, as some part of therecording process degrades, for example, in the production of the tapeitself, evaluator 171 may fail a tested unit because the parameter ofinterest lies outside the limits set by limits setter 166, even thoughanalysis of that parameter shows that it is within acceptable industrystandards according to standards table 162. Knowing the relationshipbetween the manufacturing process for the tape and the particularparameter tested, immediate corrective action can be taken. Otherwise,such a defect, especially in combination with other defects, couldrender the product (tape in this example) unusable, and such knowledgewould come to the attention of the manufacturer after the fact, i.e.,after receiving many complaints by its customers.

Details of the functional blocks in FIG. 24 after analyzer 158 are notgiven in this description, since it should be clear to one skilled inthe art what kind of off-the-shelf components should be selected to makeand use the same. For example, standards table 162 can be in the form ofany of a variety of available read-only memory devices, parameter list164 and signature store 168 can be random access memory devices, andlimits setter 166 could be in the form of a simplified microprocessorwhich applies percentage limits or plus and minus values from aparticular value entered. Evaluator 171 may be implemented in some formof sophisticated comparator in which each of a large number of parametervalues from analyzer 158 is compared with a pair of numbers for eachsuch value stored in signature store 168, the two values from signaturestore 168 being upper and lower limits within which the parameter beingevaluated must fall. The evaluation output signal is then a printedtable of data showing a list of parameters, the tolerances establishedby limits setter 166, the value of each parameter being evaluated byevaluator 171, and out-of-tolerance limits information. A sample of atable so constructed is shown in Tables I, II, and III which are moreclosely associated with the "disc evaluation" shown in FIG. 25.

Referring to FIG. 25, the "disc evaluation" scheme is represented. Here,the same components are shown as were shown in FIG. 24 with the additionof the disc mastering recorder 173 and associated functional blocks. Inthis scheme, evaluator 171 evaluates the tape signature stored insignature store 168 relative to the corresponding disc signature storedin signature store 231. When pre-mastering tape 154 is played in player156, assuming that a tape "signature" has been acquired as described inconnection with FIG. 24, the program material and test tones aretransferred to video disc 177 by disc mastering recorder 173. It is tobe noted that both lead-in and lead-out signals are transferred to thevideo disc 177 along with program material in order that analysis of adisc can be performed using the same test signal sources as thoseassociated with the pre-mastering tape. Blocks 217 through 223represents the major process steps in the production of a video discfrom exposure and development in block 217 through applying adhesive andputting together the two disc halves to form a completed two-sided discin block 223. A disc player 224 then plays the completed disc, and theresults are analyzed in analyzer 226 in a manner similar to that ofanalyzer 158. Again, it is preferable to compare the output of analyzer226 with fixed standards from a standard's table 227 in a comparator225. This kind of preliminary checking eliminates those discs whichmight contain defects causing the parameters tested to be very far outof acceptable industry standard limits. Additionally, and common to allevaluation schemes in FIGS. 24-27, performing this initial analysisagainst "world" standards is a check on the quality of a customer'soriginal material, and this can be of great benefit when deviations fromsuch "world" standards can be detected early, e.g., before discmastering is initiated.

In any event, assuming the results of analyzer 226 are tolerable againstfixed industry standards, the analyzer results are sent to signaturetable 229 and stored in signature store 231. Recalling that the lead-inand lead-out test tones are accumulated in real time in less thanone-half second and that certain audio and video tests are performed onthe active program material, under manual or computer control, evaluator171 recalls the tape signature from store 168 and the disc signaturefrom store 231 and compares parameter-for-parameter the two signatures.Again, a visual display or hard print readout is available to show howwell the particular disc has performed against its pre-masteringcounterpart (reference again Tables I, II and III).

The importance of measuring like parts of the copy and master has beenmentioned previously, and the logic and wisdom of this is ratherobvious. Accordingly, in addition to the "signature" containingparameter analysis results and tolerance range limits, it is essentialthat the "tape signature" comprise in its make-up the particular framenumbers at which video and audio active program analysis is to takeplace. In this manner, the "personality" of a "signature" is totallycharacterized with all of the information to make a signature comparisonat any time and at any step in the process, in FIG. 25, for example, themaster disc has a photoresist layer at point A in the process, isexposed and developed at point B, metalized at point C, made into astamper at point D to produce a one-sided (1X) plastic replica at pointE, provided with a reflective coating at point F, and a protectivecoating at point G, and finally, combined with a second-half disc toform a completed disc (2X) at point H.

It is important to note at this point that, as with any replicatingprocess, some degradation of the program material through each step ofthe process can be expected at points A-H. Furthermore, the degradationto be expected between points A and B may be less than that expectedbetween points B and C, etc. Accordingly, an application of the presentinvention concerns playing the disc from any point in the process andestablishing a "signature" for each of the points A through H. Theinvention thus provides substantially "real-time" evaluation forcorrelation with "in process" activities to cause supervisorialpersonnel to shut down or modify equipment before any great loss ofmaterial and employee time. Additionally, out-of-tolerance parametertrends can be readily sensed, and the information gathered by comparingprocess signatures at each step in the process, so as to improvespecific manufacturing processes or process steps due to the highlyaccurate and repetitive objective testing capabilities that "signature"testing provides. Such trend information can be used to foreseepotential problems, even though on an absolute scale, the parameterstested are within acceptable limits. Finally, by varying the processparameters at each major step in the process, product improvement can beenhanced by observing the "signature" comparisons when temperatures,pressures, process times, etc., are varied.

Concerning "disc evaluation", in view of the fact that video discplayers are of recent design, the present invention can be used inevaluating player consistency. For example, instead of changing discs inFIG. 25, the same disc can be played back on a number of disc players224, and a "signature" of the players can be developed and compared withthe "signature" established from a known good player.

The use of this invention with "throughput" devices, such as audio andvideo amplifiers and special effects devices, i.e., echo units,distribution amplifiers, limiters, and the like, has been mentionedearlier. Since information can be deposited on a recording medium, andthe invention can recover and make performance tests on the recoveredinformation, it is equally possible to extend the practical applicationof this invention to such throughout devices by merely applying the testsignals that would normally be recorded on a recording medium to theinput of the throughput device, sensing the output of the throughputdevice in substitution for the signals normally recovered from therecording medium, and making the same comparisons that would be made toevaluate the quality of signal transfer in the record/playback process.Thus, various electrical characteristics of the throughput device can bemeasured and automatically analyzed and evaluated. FIG. 26 shows such ascheme.

Since the evaluation procedure requires preparing a "signature" of athroughout reference unit 234, a separate path for a throughput undertest 235 is shown in FIG. 26. The unit under test is shown to have itsown analyzer 226, signature table 229, and signature store 231. Ofcourse, in the interest of economy, a scheme similar to that of FIG. 224could also have been used, wherein analyzer 158 could be time sharedwith the referenced unit 234 and unit under test 235. In such a case,analyzer 226, signature table 229, and signature store 231 would beunnecessary.

Likewise, in case of need, rather than taking the output of analyzer 158in FIG. 24 directly to evaluator 171, a separate analyzer, signaturetable, and signature store as in FIG. 26 could have been used.

Finally, FIG. 27 illustrates the manner in which digital signatureevaluation is accomplished. The same analogy follows in this figureinsofar as forming a signature in store 168. However, whether the signalto be evaluated is audio or video, a player, termed device under test238, outputs its signal to the A/D converter 237, and the digital formof the signal is stored in digital memory 233. If necessary, as was withthe audio test tones during lead-in and lead-out, a recirculate control240 feeds back the selected digital portion of the stored signal in aloop around fashion so as to output a continuous version of the storedsignal to D/A converter 239. The analog version of the signal is thenanalyzed in analyzer 226, a signature table is established, and theanalyzing results are stored in signature store 231 for later evaluationin comparator 171.

Table I is a printout of the results of "signature" evaluation duringlead-in of a video disc. The selected parameters analyzed for the discexample used are listed in the lefthand column, and the "signature"comparison is shown in the two groups of three columns each, one groupfor audio channel 1 and another group for audio channel 2. The centercolumn for each channel lists the value of the disc analysis measurementfor each parameter, while the two values on either side of the centercolumn indicate the "signature" limits set by limits setter 166 of FIG.25.

Table II shows similar evaluation comparison results for lead-out of thedisc under test.

In like manner, Table III shows the video evaluation test results. Here,an additional column of information is shown, that of actual tapeanalysis measurements from which upper and lower limits for the"signature" comparison were generated in limits setter block 166.

                                      TABLE I                                     __________________________________________________________________________                               AUDIO/VIDEO QUALITY                                                           MONITORING SYSTEM                                                             AUDIO DATA ANALYSIS                                                                             TIME: 16:01:52                                              FOR DISC          DATE: 12/30/81                   DISC ID - 050148010        LOWER        UPPER                                                                              LOWER        UPPER               AVOID TEST (LEAD IN) UNITS TAPE 1                                                                             CH 1 DISC                                                                             TAPE 1                                                                             TAPE 2                                                                              CH 2                                                                                 TAPE                __________________________________________________________________________                                                              2                   TEST FRAME 1                                                                  FREQUENCY            HZ    900.00                                                                             991     1100.00                                                                            900.00                                                                              999    1100.00             AC LEVEL             DMV   -12.21                                                                             -7.19   -4.07                                                                              -12.11                                                                              -3.07  -4.04               SINAD                DB    22.70                                                                              28.28   34.06                                                                              12.00 13.00  11.00               SINAD WITH FILTER    DB    27.94                                                                              31.04   34.14                                                                              14.40 15.00  17.60               TOTAL HARMONIC DISTORTION                                                                          %     1.80 3.8     2.20 2.43  18.1   2.77                DC LEVEL             VOLTS -.01 -.008   -.01 .03   .029   .04                 PHASE ANGLE AT 1 KHZ DEG   2.61 1.57    2.61 2.03  1.07   2.03                TEST FRAMES 2 AND 3                                                           CROSSTALK                                                                     CROSSTALK FREQUENCY  HZ    831.25                                                                             904     918.75                                                                             38.95 41     43.05               CROSSTALK AC LEVEL   DB    -39.87                                                                             -28.36  -32.63                                                                             -39.02                                                                              -36.44 -31.92              TEST FRAME 4 AND 7                                                            SIGNAL/NOISE RATIO   DB    41.43                                                                              38.85   50.63                                                                              33.03 37.09  40.37               SIGNAL/NOISE RATIO WITH FILTER                                                                     DB    50.57                                                                              47.56   61.81                                                                              44.02 48.18  53.80               TEST FRAMES 5 AND 6                                                           INTERMODULATION DISTORTION                                                    AMPLITUDE 7 KHZ      DB    -21.34                                                                             -19.4   -17.46                                                                             -23.65                                                                              -21.5  -19.35              AMPLITUDE 7 KHZ + 60 HZ                                                                            DB    -52.14                                                                             -46.6   -42.66                                                                             -51.81                                                                              -46.0  -42.39              AMPLITUDE 7 KHZ - 60 HZ                                                                            DB    -47.63                                                                             -43.1   -38.97                                                                             -50.05                                                                              -45.0  -40.35              TEST FRAMES 8 THROUGH 12                                                      FREQUENCY RESPONSE AT -15 DB                                                  -3 DB AUDIO BANDWIDTH (KHZ)                                                   __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________                               AUDIO/VIDEO QUALITY                                                           MONITORING SYSTEM                                                             AUDIO DATA ANALYSIS                                                                             TIME: 16:01:52                                              FOR DISC          DATE: 12/30/81                   DISC ID - 050148010        LOWER        UPPER                                                                              LOWER        UPPER               AVOID TEST (LEAD IN) UNITS TAPE 1                                                                             CH 1 DISC                                                                             TAPE 1                                                                             TAPE 2                                                                              CH 2                                                                                 TAPE                __________________________________________________________________________                                                              2                   TEST FRAME 1                                                                  FREQUENCY            HZ    900.00                                                                             990     1100.00                                                                            900.00                                                                              991    1100.00             AC LEVEL             DMV   .18  .38     .53  -11.75                                                                              -7.79  -3.12               SINAD                DB    20.14                                                                              27.17   30.20                                                                              21.03 26.42  31.55               SINAD WITH FILTER    DB    24.45                                                                              29.27   29.89                                                                              25.73 28.79  31.45               TOTAL HARMONIC DISTORTION                                                                          %     2.16 4.4     2.64 2.07  4.8    2.63                DC LEVEL             VOLTS -.01 -.007   -.01 .02   .024   .01                 PHASE ANGLE AT 1 KHZ DEG   5.76 5.28    5.76 2.03  2.03   2.03                TEST FRAMES 2 AND 3                                                           CROSSTALK                                                                     CROSSTALK FREQUENCY  HZ    710.60                                                                             913     795.40                                                                             38.95 149    43.05               CROSSTALK AC LEVEL   DB    -39.64                                                                             -36.56  -32.44                                                                             -35.05                                                                              -34.62 -28.67              TEST FRAME 4 AND 7                                                            SIGNAL/NOISE RATIO   DB    40.70                                                                              37.41   49.74                                                                              42.54 35.34  32.00               SIGNAL/NOISE RATIO WITH FILTER                                                                     DB    47.40                                                                              46.27   57.94                                                                              50.00 47.59  61.12               TEST FRAMES 5 AND 6                                                           INTERMODULATION DISTORTION                                                    AMPLITUDE 7 KHZ      DB    -22.22                                                                             -20.1   -18.18                                                                             -23.21                                                                              -21.1  -18.97              AMPLITUDE 7 KHZ + 60 HZ                                                                            DB    -43.34                                                                             -39.0   -35.46                                                                             -45.76                                                                              -41.4  -37.44              AMPLITUDE 7 KHZ - 60 HZ                                                                            DB    -42.90                                                                             -38.3   -35.10                                                                             -45.54                                                                              -40.2  -37.26              TEST FRAMES 8 THROUGH 12                                                      FREQUENCY RESPONSE AT -15 DB                                                  -3 DB AUDIO BANDWIDTH (KHZ)                                                   __________________________________________________________________________

                                      TABLE III                                   __________________________________________________________________________           AUDIO/VIDEO QUALITY MONITORING SYSTEM   TIME: 15:54:37                        VIDEO DATA ANALYSIS FOR DISC            DATE: 12/30/81                 STARTING                            TAPE DISC  TAPE TAPE  EXCEP-              FRAME 3                                                                              DISC ID - 050148010001                                                                              UNITS  LOWER                                                                              ACTUAL                                                                              UPPER                                                                              ACTUAL                                                                              TION                __________________________________________________________________________    810    AVG PIC LEVEL         % FRAME                                                                              19.80                                                                              22.00 24.20                                                                              22.00                            COMPOSITE VITS                                                                BAR AMP               IRE    95.75                                                                              100.00                                                                              106.05                                                                             101.00                           SYNC AMP              % BAR  -39.05                                                                             -35.00                                                                              -31.95                                                                             -35.50                           BURST AMP             % BAR  10.70                                                                              24.40 32.10                                                                              21.40                            CMRD-LUM GAIN         %      -39.00                                                                             -25.50                                                                              -13.00                                                                             -26.00                           RELATIVE BURST GAIN   %      2.70 16.10 8.10 5.40  ***                        RELATIVE BURST PHASE  DEG    3.50 25.89 10.50                                                                              7.00  ***                        DIFF GAIN             %      12.10                                                                              38.80 36.30                                                                              24.20 ***                        DIFF PHASE            DEG    4.59 17.30 5.61 5.10  ***                        LUM NON-LINEAR DISTORTION                                                                           %      5.75 17.20 17.25                                                                              11.50 ***                        CHRD-LUM DELAY        NSEC   57.50                                                                              120.00                                                                              172.50                                                                             115.00                           LINE-TIME DIST        %      2.16 2.70  3.24 2.70                             PULSE TO BAR RATIO    %      2.74 3.90  3.41 3.10  ***                        2T-PULSE RINGING      % RF   1.75 3.40  5.25 3.50                             T-STEP RINGING LD     % BAR  11.00                                                                              26.40 33.00                                                                              22.00                            T-STEP RINGING TR     % BAR  8.50 16.40 25.60                                                                              17.00                            COMBINATION VITS                                                              WHITE FLAG AMP        IRF    58.83                                                                              99.90 101.57                                                                             93.70                            MP 400 KHZ            % FLAG 45.90                                                                              53.00 62.10                                                                              54.00                            MP 1.0 MHZ            % FLAG 39.95                                                                              49.00 54.05                                                                              47.00                            MP 2.0 MHZ            % FLAG 39.10                                                                              45.00 52.90                                                                              46.00                            MP 3.0 MHZ            % FLAG 35.70                                                                              42.00 48.30                                                                              42.00                            MP 3.5E MHZ           % FLAG 28.90                                                                              29.00 37.10                                                                              34.00                            MP 4.2 MHZ            % FLAG 18.70                                                                              21.00 25.30                                                                              22.00                            CHRD NON-LIN GAIN 20 IRE CHROMA                                                                     IRE    20.43                                                                              18.70 24.97                                                                              22.70                            CHRD NON-LIN GAIN 80 IRE CHROMA                                                                     IRE    38.43                                                                              39.20 46.97                                                                              42.70                            CHRD NON-LIN PHASE    UFG    95.15                                                                              177.00                                                                              285.45                                                                             190.30                           CHRD-LUM INTERMOD     IRE    .45  .90   1.35 .90                              VIRS                                                                          VIRS SET UP LEVEL     IME    3.55 6.80  10.65                                                                              7.10                             VIRS BLANKING LEVEL   % CARR                                                  VIRS WHITE LEVEL      % CARR                                                  HORIZ BLANKING WIDTH  USEC   10.22                                                                              11.33 12.48                                                                              11.35                            HORIZ SYNC WIDTH      USEC   4.29 4.69  5.23 4.76                             HORIZ SYNC RISE TIME  NSEC   140.00                                                                             250.00                                                                              420.00                                                                             280.00                           HORIZ SYNC FALL TIME  NSEC   24.64                                                                              180.00                                                                              73.92                                                                              49.23 ***                        SYNC SETUP            USEC   8.68 9.53  10.60                                                                              9.64                             FRONT PORCH DURATION  USEC   1.28 1.49  1.56 1.42                             SYNC TO BURST STAFT DURATION                                                                        USEC   4.96 5.43  6.06 5.51                             COLOR BURST WIDTH     CYCLES 4.10 8.60  9.90 9.00                             MISCELLANEOUS                                                                 VERTICAL BLANKING WIDTH FLD 1                                                                       LINES  16.92                                                                              18.79 20.66                                                                              18.79                            VERTICAL BLANKING WIDTH FLD 2                                                                       LINES  16.92                                                                              18.79 20.66                                                                              18.79                            EQUALIZING PULSE WIDTH                                                                              USEC   2.07 2.30  2.53 2.30                             SERRATION WIDTH       USEC   4.14 4.65  5.06 4.60                             SIGNAL TO NOISE-FRAME DB     -63.45                                                                             -33.94                                                                              -21.15                                                                             -42.30                           SIGNAL TO NOISE-FIELD 1                                                                             DB     -62.46                                                                             -33.07                                                                              -20.86                                                                             -41.71                           SIGNAL TO NOISE-FIELD 2                                                                             DB     -63.90                                                                             -33.90                                                                              -21.30                                                                             -42.60                    __________________________________________________________________________

Another application for the present invention concerns video discmastering machines known in the art as direct-read-after-write machines.An example of such a mastering machine can be found in U.S. Pat. No.4,225,873, issued Sep. 30, 1980, filed Feb. 20, 1973, to Winslow. Adirect-read-after-write disc is known from U.S. Pat. No. 4,264,911,issued Apr. 28, 1981, filed Aug. 20, 1979, to Wikinson. In such asystem, a high-powered laser beam is focused through an objective lensand split into two paths. A high-powered laser beam path is used to"burn" holes in a metallic coating on the disc surface, while thesecond, lower-powered beam path is directed downstream of the directionof movement of the disc and is used as a read beam for immediatelyreading the information recorded by the high-powered beam. Since thebeam points of impact on the disc are separated by only a few microns,and with the disc rotating at 1800 rpm, a substantially simultaneoussignal can be retrieved as the disc is being "written". Since audio testtones in lead-in are recovered in less than one-half second, and sinceanalysis of the active audio and active video portions of the programmaterial commence (or can commence) at frame 1, when comparing theoutput signal developed by the low power laser beam with a previouslyderived signature from the pre-mastering tape, in the event thatblemishes are encoutered in the process of recording the disc, suchdefects can be substantially instantaneously derived so as to eliminatethe need for wastefully proceeding with perhaps a further one hour ofrecording time.

In this connection, the twelve segments of audio lead-in tones areretrieved at the rate of 30 segments per second (vertical frame rate),and instruments such as the Hewlett Packard 8903A Audio Analyzer areavailable which can measure a given parameter in typically 2.5 secondsor less. Since each segment of the lead-in test tones is used for morethan one audio measurement, it is recirculated, as explained earlier, toproduce a continuous version thereof for the length of time necessary toperform all audio measurements by the analyzer before going on toretrieving and continuously looping the second test segment. The tablebelow, Table IV, indicates which audio measurements are made in eachtest frame.

TABLE IV

Test Frame 1

Frequency

AC Level

AC Level With Filter

SINAD

Distortion

DC Level

Distortion Level

Distortion Level With Filter

SINAD With Filter

Signal/Noise Ratio

Signal/Noise Ratio with Filter

Test Frames 2 and 3

Frequency

AC Level

Test Frames 4 and 7

Frequency

Distortion

Distortion Level

Distortion Level With Filter

Signal/Noise Ratio

Signal/Noise Ratio with Filter

Test Frames 5 and 6

Amplitude 7 kHZ

Amplitude 7 kHZ+60 HZ

Amplitude 7 kHZ-60 HZ

Test Frames 8-12

Frequency Response

Since the largest number of measurements made at any one test frame(test frame 1) is 11, and since the available analyzer can perform itsanalysis in 2.5 seconds or less, the maximum length of time necessaryfor the analyzer to make all measurements in test frame 1 is about 27.5seconds. Accordingly, the recirculate control 99 shown in FIGS. 9 and 12need only recirculate the tone segment for a maximum time of 27.5seconds. Furthermore, and although the present invention is not limitedto the specific tests listed above, to complete all 23 audio testmeasurements would require no more than 57.5 seconds. Conservativelythen, the repetition rate at which the complete audio measurement cycleis repeated can be one cycle every minute. Then, since the longestactive program test is the mono/non-mono check, and since this check canbe completed each 65.5 seconds, it is clear that advantage can be takenof the AVQMS system to weed out defective discs in only a few minutes ofrecording/playing time. This concept can be carried out on video discsproduced by the method illustrated in FIG. 25 (as opposed to the directread-after-write process) so as to be able to detect defective discs atany point along the process in only a few minutes. Of course, defectsnot contained close to the lead-in portion of the disc being evaluatedwill not show up instantaneously, but process defects which casueuniform parameter degradation throughout the video disc will be caughtin the first couple of minutes of playing time. Furthermore, the speedat which information can be analyzed with the AVQMS eliminates much timetaken in manually observing and/or manually taking measurements underprior techniques. Then again, all subjective evaluation of the disc iseliminated.

A finer point of distinction between objective testing and subjectivetesting can be appreciated from the fact that at certain points in theprocess of producing a disc in accordance with FIG. 26, it may beexpected that the parameters being tested will not be subjectivelyacceptable, but will be objectively acceptable. This is best explainedwith reference to the fact that after exposing and developing in block217 of FIG. 25, the disc produced at point B in the process issubstantially clear, being comprised of a glass substraight anddeveloped photo resist material. When bombarding the disc surface with aread laser beam for purposes of developing a signal therefrom, it can beappreciated that the contrast between exposed and non-exposed portionsof the disc surface is not great, especially as compared with a finaldisc surface which contains a highly reflective metal coating forreflecting a substantial portion of the read beam back from the planarsurfaces and scattering a substantial portion in the non-planarportions. Accordingly, in reading the disc at point B in the process, asmaller signal-to-ratio in both audio and video measurements can beexpected. However, since the system according to the present inventioncan develop its own "signature". Acceptable signal/noise figures can beextrapolated from expected final results to gauge the acceptable limitsfor the earlier steps in the process. Thus, a low signal-to-noise ratioat point B is predictable and acceptable for that particular point inthe process, even though the signal-to-noise figure measured would notfall within an acceptable range for the final product.

Only preferred embodiments of the invention have been described above.One skilled in the art, however, will recognize that where audio signalmeasurements were made in the manner of FIGS. 7-12, clearly video signalmeasurements, custom or standard, can be performed in a similar manner.That is, the present state of the art of video processing includesdigitizing video signals, storing same, and reading out the storedsignals at will. An example is the broadcast quality Time BaseCorrectors available from many different manufacturers. Thus, recordingshort segments of video test signals during lead-in and lead-out,playing them back in real-time, storing the retrieved signals digitally,recalling a selected segment and recirculating it for purposes ofcreating a continuous representation of the selected segment foranalysis and evaluation, are techniques well within the restraints ofpresent technology once the artisan has disclosure of the presentinvention before him or her. Accordingly, the manner of multiplexing andsubsequent analyzing of the audio lead-in and lead-out tones are to betaken as representing a preferred form of the invention, and the blockslabelled with "audio" designations merely need being renamed toillustrate the eqivalent manner of multiplexing and subsequent analyzingof the lead-in and lead-out for video qualities (with appropriatechanges of signal sources and timing figures, of course.)

Similarly, the manner in which video parameter analysis and evaluationhave been described herein could, with like analogy, apply to theanalysis and evaluation of audio parameters.

While the invention has been particularly shown and described withreference to a preferred embodiment and alternations thereto, it is tobe understood by those skilled in the art that various changes in formand detail may be made therein without departing from the spirit andscope of the invention.

We claim:
 1. A method of evaluating recording characteristics of arecording medium, comprising the steps of:(a) recording, in real time, atimed sequence of contiguous test signals on said medium with each testsignal lasting for a time T; (b) playing back, in real time, therecorded test signals and storing a representation of each said testsignal in memory; (c) selectively recalling one of said test signalslasting for a time T, and repeatedly recirculating said selected onetest signal through memory to produce a continuous representation ofsaid selected test signal; and (d) performing analysis upon saidcontinuous representation of said selected test signal.
 2. A method asset forth in claim 1, wherein the step of storing includes the step ofconverting the recorded test signals from analog signals to digitalsignals.
 3. A method as set forth in claim 2, wherein the step ofrecirculating includes the step of converting the digital signals toaudio signals.
 4. A method as set forth in claim 3, wherein the step ofperforming analysis includes the step of analyzing by a signal analyzerand by a spectrum analyzer.